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AN EXPERIMENTAL^ 
STUDY OF SLEEP 



(From the Physiological Laboratory of the 
Harvard Medical School and from Sidis' Laboratory) 





{A 



BY 



BORIS SIDIS, M.A., Ph.D., M.D. 

Author Of PSYCHOPATHOLOGICAL RESEARCHES //" 

in Mental Dissociation 




BOSTON: RICHARD G. BADGER 

XTbe (Borbam press 

1909 



m v 



Copyright 1908 by Boris Sidis, M.D. 
All Rights Reserved 



^ 



t> 



,^> 



"9 



LIBfjARY Of CONGRESS 
Two Copies Received 

DEC 22 1808 

_ Copyritfni tntry 
CLASS CX XXt, No. 
COPY \ . * U 



Gbe $orbam press, JSoston, Ta. 5. B. 



TO 
DR. MORTON PRINCE 

in appreciation of his originality in Philosophy and 
Psychology and of his staunch friendship towards 

THE AUTHOR. 



CONTENTS 



Part I — Experimental 



Chapter 


I. 


Introductory Remarks . 


I 


Chapter 


II. 


Theories of Sleep 


3 


Chapter 


III. 


The Conditions of Sleep 


9 


Chapter 


IV. 


Intermediary States 


14 


Chapter 


V. 


The Induction of Sleep States 


. 19 


Chapter 


VI. 


Experiments on Frogs . 


21 


Chapter 


VII. 


Experiments on Guinea-Pigs 


. 29 


Chapter 


VIII. 


Experiments on Cats 


• 33 


Chapter 


IX. 


Experiments on Dogs . 


• 39 


Chapter 


X. 


Experiments on Children 


• 54 


Chapter 


XI. 


Motor Reactions of -Lnfants, Childrer 


l and 



Adults in Subwaking and Sleeping States 67 



Part II — Theoretical 



Chapter XII. 

Chapter XIII. 
Bibliography 



Cell Energy, Threshold, " Stimulus-Exhaus- 
tion " and Sleep ..... 

Motor Consciousness and Sleep . 



75 
9i 
99 



PART I 
EXPERIMENTAL 



Hypotheses non fingo" 

— Newton. 




AN 



EXPERIMENTAL 



STUDY OF SLEEP 



Chapter I 

Introductory Remarks 

WRITERS on sleep complain that little attention 
has been paid to the subject, that it is sufficient 
to open a text-book on physiology to be con- 
vinced of the fact that the physiology of sleep 
is almost entirely neglected, inasmuch as the school-physi- 
ologist usually dismisses the subject with a few phrases, 
often quite general and devoid of meaning. It is quite true 
that while one cannot as a rule be satisfied with the imperfect 
state of textbook-physiology which usually lingers in the hind 
ranks of the battle-ground of science, still one cannot blame 
the text-books for avoiding such a delicate subject, the 
nature of which is so uncertain and so highly problematic. 
In addition to the uncertainty of the subject of which 
the more conservative of school-physiologists fight shy, there 
seems to be an ill defined feeling which is not without some 
good foundation, namely, that sleep is not entirely a physio- 
logical subject, that sleep presents some very important 
aspects that need be taken into consideration which the 



2 An Experimental Study of Sleep 

physiologist is unable to deal with by his usual methods 
and from his standpoint alone. 

Moreover there may be another reason for the indif- 
ference of school-physiology to a subject which is otherwise 
of such a vital importance in the whole domain of animal 
life. Man is more interested in active than in passive 
states. It is therefore natural that the physiologist should 
devote his attention more to waking life than to sleeping 
states. Besides, physiology dealing essentially with activi- 
ties and functions tends to ignore states which are usually 
regarded as the very acme of inactivity. With the advance 
however of biological, physiological and psychological 
sciences even states of passivity can no longer be ignored, — 
their conditions, causation and nature must be studied and 
closely investigated, especially if those states are found 
present throughout the ascending line of animal life. The 
conditions for the study of sleep become all the more favor- 
able as we reach man. We find that sleep-states in man's 
life are no longer instable and taken by snatches, because the 
watchfulness requisite in wild-life under the constant strain 
of the struggle for existence no longer obtains. In man's 
life sleep-states become more or less organized, systematized 
and are no longer disturbed, — they alternate rhythmically 
with waking states. More than one-third of man's life is 
passed in sleep, — it seems that this fact alone should 
indicate the importance of sleep-states in man's cycle of 
biological and physiological processes and should arouse 
the interest of the scientific investigator. As a matter of 
fact some scientific thinkers have given the subject of sleep 
a good deal of their attention. Although text-book physi- 
ology passes over the subject with a few meaningless phrases, 
the literature of sleep is really very extensive. It may be 
well before we proceed with the exposition of our own 
observations and experiments on sleep to give first a brief 
review of the chief theories on sleep. 



Chapter II 

Theories of Sleep 

FROM the very earliest times man wondered about 
sleep and attempted some explanation of it. It 
was supposed that in sleep the soul wanders away 
from the body and leaves it in a lifeless condition. 
Many of the savage tribes are on that account afraid to 
waken people lest the soul may be frightened away and not 
return at all to the body. That is why even at present we 
often hear the saying that sleep is the companion of death. 
On the other hand death is often described as sleep. On 
the same basis dreams were explained by the primitive 
mind, — the soul in sleep leaves the body and wanders 
away; on its wanderings the soul meets with all kinds of 
adventures and it is such experience that gives rise to 
dreams. In sleep the wandering soul, not encumbered by 
the gross body, can visit great distances in a short time and 
can even communicate with heavenly powers, — with angels 
and gods. 

The impassive soul reluctant flies, 
Like a vain dream, to these infernal skies. 
Modern spiritualists adopt this ancient belief in full or 
express it as "the release of human personality from the 
subliminal. " 

The scientific theories of sleep are numerous, but they 
can be reduced to a few main types. This reduction will 
help the reader to become oriented in the vast literature that 
has gathered about the subject. The theories of sleep may 
be classified as follows: 

theories, which may be sub- 



I) 


The Physiological 




divided into: 




a) Mechanical 




and 




b) Chemical 


2) 


Pathological 


3) 


Histological 


4) Psychological 


5) Biological 



4 An Experimental Study of Sleep 

The mechanical theories are of the circulatory variety 
and are usually much favored by physicians, — they attempt 
to explain sleep by changes in the blood circulation of the 
cerebrum. As far back as the eighteenth century the theory 
of sleep greatly in vogue among the physiologists was — 
congestion of the brain favored by the position of the head. 
This view was entertained by Haller, J. Miiller, Hartley and 
others. Cappie has somewhat enlarged on it, inasmuch 
as he ascribes sleep to the venous congestion of the brain. 
This congestion of blood was supposed to bring about pres- 
sure on the brain with the result of depression of all the 
cerebral functions. The great psychologist Hartley sum- 
marises the physiological theories of his time thus: "It 
appears then that during sleep the blood is accumulated in 
the veins and particularly in the venal sinuses which surround 
the brain and spinal marrow. . . . And it is agreeable 
to this that in most dissections after lethargies, apoplexies, 
etc., the venal sinuses of the brain and consequently those 
of the spinal marrow which communicate freely with them 
are particularly full. ... It follows therefore that the 
brain and spinal marrow will be particularly compressed 
during sleep, since the blood then takes up more space, is 
particularly accumulated within the cavities of the skull 
and vertebrae, and the hardness of these bones will not 
suffer them to yield or make more room. ... In short 
this compression will result in sleep." These generalizations 
were favored by observations on the famous case of the 
Parisian beggar whose injured skull gave the opportunity 
to observe the rise and fall of the exposed cerebrum in the 
waking or sleeping state. Recently Mosso claimed the 
same causation of sleep and on similar observations. As 
to the circulatory changes proper, two opposing views have 
been taken. Some, such as Durham, CI. Bernard, Kussmaul 
Howell, Lehman, de Fleury ascribe sleep to cerebral anemia. 
Others again, such as Brown, Czerny, Broadman maintain 
that sleep is due to cerebral hyperemia. Claperede in 
reviewing the circulatory theories of sleep quotes Richet's 
apt criticism: "Sleep and waking states bring about all 
kinds of changes in cerebral circulation depending but little 
on the position of the head. Birds whose hemispheres have 



An Experimental Study of Sleep 5 

been removed still present the same changes of sleep and 
waking. Biologically regarded, sleep is a far more general 
phenomenon than that of the presence of a brain irrigated by 
a blood circulation. Finally the activity of a tissue is not 
entirely dependent on the amount of blood circulating in it." 
There are however still more cogent objections to such 
theories of sleep, objections which clearly show the incon- 
gruence of the circulatory theories. We shall point them 
out further in our present study. 

We may turn now to the chemical theories which are 
far more favored by the conservative physiologist, inasmuch 
as they fall in with what the physiologist regards as more 
scientific. With the experiments of Pettenkofer and Voit 
on the respiratory quotient new life was injected into sleep 
theories. Those two investigators have found the respiratory 
quotient ^ is diminished during sleep. The tissues 
absorb relatively more oxygen during the day than during 
the night. This fact of the using up and impoverishment of 
blood of intermolecular oxygen started new life in the theories 
of sleep. Pfliiger, Sommer and others attempted to work 
out a scientific theory of sleep based on research of the bio- 
chemistry of the cell and the intermolecular activity of the 
oxygen-molecule or atom. Pfliiger's authority lent vitality 
to this view so that even Heubel whose theory of sleep is 
really psychological in character tries to shelter it under 
Pfliiger's physiological wings. 1 

With the chemical theories we pass by degrees into the 
pathological theories of sleep. Already in the early part of 
the nineteenth century Marshall Hall proposed the view that 
sleep was a kind of epilepsy. This view however met with 
little favor, because of lack of facts to support it. With the 
advance of chemistry and of its application to physiological 
research, and especially with the rise of the modern views of 
the role of autointoxication and toxins in diseases, the patho- 
logical theories of sleep were resuscitated under the new 
guise of autointoxication. Obersteiner and Preyer launched 
the theory that sleep was arTautointoxication of the system 
by toxic matters accumulating in the blood, due to the 

1 We may possibly refer to Loeb's work on heliotropism and sleep of butterflies as 
an example of a purely bio-chemical view of sleep. See Dec. Public Univ., Chicago, V. I. 



6 An Experimental Study of Sleep 

activity of the various tissues. Lactic acid was supposed 
to be the particular substance in question. Others such as 
Dubois ascribed the same state to the accumulation of 
carbonic acid. These were followed by a host of writers 
such as Binz, Errero, Bouchard, Breisacker and others. 
The toxic and autotoxic theories of sleep enjoy quite a wide 
popularity, because they fall in with the scientific notions 
of the age. Those theories would make of sleep a patho- 
logical state, but the facts are against such a view. 

By the middle of the nineteenth century, when physio- 
logical experiments on nerve-conduction were at their 
height, Purkinje proposed the theory that sleep might be 
due to the Interruption of neural conductivity between the 
cortical matter and the rest of the cerebrum. This view 
was further developed by Mautner, Warlomont, Oppen- 
heimer and others. As a further modification of the same 
theory, but based on more fundamental physiological 
processes may be mentioned Verworn's theory which refers 
sleep and waking-states to processes of assimilation and 
dissimilation going on in the organism. At the same time 
with Verworn, Van Gieson and Sidis worked out their theory 
of sleep, basing it on similar processes, namely on anabolism 
and catabolism and developing the interrelation of waking 
and sleeping states with the symptom complexes of nervous 
and mental diseases. The theory of Van Gieson and Sidis 
is based on the variability of different levels of neuron 
energy. We may dismiss this latter theory in a few words 
as we shall discuss it in our study. We can only say here 
that the theory is essentially based on the concept of neuron- 
energy. 

This brings us close to the famous theories of retractility 
of neuron-elements which have been of late utilized by many 
writers for various purposes. The development of the 
histology of the nervous system and especially of neuro- 
pathology have brought new life to the solution of the prob- 
lem of sleep. The biological investigations of the cell by 
Kolliker, Remak, Nageli, Hoffmeister, Virchow, Max 
Schultze, Hertwig, Fol, Van Beneden, Strassburger, Heiden- 
hein, Boveri and many others opened up new horizons for 
theories of cellular activities. Naturally the sleep theories 



An Experimental Study of Sleep 7 

came in for their share. It was not however until the 
researches of Golgi and Ramon Y Cajal had laid the 
foundation for their famous doctrine of independence and 
contiguity of neural elements that the theories of sleep could 
seize on some tangible anatomical facts and work them for 
their benefit. Ramon Y Cajal was the first to advance 
the view that the~ neuroglia-cells by their expansions and 
contractions bring about dissociations and associations of 
the neural elements with the consequent loss or reappear- 
ance of normal waking-states. A somewhat different, but 
closely analogous theory was launched into the scientific 
world by Mathias-Duval. Instead of the retractility of 
neuroglia cells proposed by Cajal, Duval advanced the view 
that the neurons and their protoplasmic processes are 
endowed with contractility or retractility and that the func- 
tioning and loss of functioning of neural elements are due 
to contractions and expansions of the protoplasmic processes 
of the neurons. Demoor, Pupin, Berger and others have 
enlarged on this hypothesis. At first even Verworn accepted 
this hypothesis, although he discountenanced it afterwards. 
Sidis assumed provisionally the same hypothesis for abnor- 
mal dissociative manifestations, but refused to accept it as 
an explanation for the phenomena of sleep which do not 
warrant the assumption of such hypothesis. 

The psychological theories of sleep date from antiquity. 
The popular explanation is very simple, — it is a description 
of the phenomena, a description which the popular mind 
often takes for an explanation of the phenomena in question. 
Sleep is an abeyance of mental life, sleep is a rest of con- 
sciousness. Modern physiologists and psychologists who 
maintain the psychological theory of sleep have not much 
improved on that statement. The only modern substitute is 
that of inhibition. Brown-Sequard, Wundt^ Siemens, Forel, 
Oscar Vogt, all in different scientific phraseology refer 
sleep to inhibition of cerebral activity, especially of the 
frontal lobes where mental activity is supposed to " reside," 
according to some authors. Manaceine in her work on 
sleep echoes this view and comes to the conclusion that 
"sleep is the resting state of consciousness." Surely it is an 
elaboration of the obvious, if one has to write a whole volume 



° An Experimental Study of Sleep 

in order to arrive at such an important conclusion. The only 
one who really made some advance in the psychological 
theory of sleep was Heubel, Privatdocent at Kiev University, 
Russia. I can say his is an excellent piece of work based on 
a series of well performed experiments. Unfortunately, 
when I started my experiments, I was not acquainted with 
the work of that investigator. I have gone over in my 
experimental research a good deal of the same work and may 
say that Heubel's experiments have been fully confirmed by 
me. Although Heubel's theory is incomplete, there is 
a good deal of truth in it and his work well deserves the 
attention of the student of sleep. His veiw may be briefly 

summarized in the following statement: Mental activity 

depends on the incoming peripheral, sensory stimulations; 
where such peripheral sensory stimulations are absent, 
mental activity is in abeyance and sleep results. In other 
words, brain activity depends on sensory activity which in 
its turn depends on peripheral stimulations. Psychologically 
stated, consciousness is a function of sensations which in 
their turn are a function of external stimuli or impressions. 
In accordance with this view a series of experiments have 
been carefully carried out by Huebel. As my own experi- 
ments were carried out on somewhat similar lines I shall 
refer again to Huebel's work, when I give an account of my 
experiments, in order to test a somewhat similar theory 
arrived at from totally different considerations, viewing the 
subject of sleep not only from a physiological and psycho- 
logical, but also from a biological standpoint. 

An altogether different departure from the usual 
theories of sleep was recently taken Jxy Claperede. He 
points out that biologically regarded, sleep has its significance 
not as a passive state, but as an active instinct, like all the 
other instincts of animal life. To put it in his own words : 
"Le sommeil n'est pas un etat purement negatif, passif, il 
n'est pas la consequence d'un simple arret de fonctionne- 
ment: il est un fonction positive, un acte de ordre reflexe, 
un instinct, qui a pour but cet arret de fonctionnement; 
ce n'est pas parce que nous sommes intoxiques, ou epuises, 
que nous dormons, mais nous dormons pour ne pas l'etre." 
This biological view of Claperede forms one of the most 



An Experimental Study of Sleep 



9 



valuable contributions to the theory of sleep. It throws 
altogether new light on the subject of sleep, and many 
obscure until now unexplained facts can be understood in the 
new light of the biological standpoint taken by Claperede. 
Claperede's physiological theory of inhibition is not as clear, 
but with some modification I think it could well harmonize 
with my views and my work on sleep. While accepting 
the views of Claperede, my standpoint taken in this study is 
based on investigations published in previous works of mine 
mainly dealing with the subject of dissociative states in 
general. 

Chapter III 

The Conditions of Sleep 

TAKING the well-known dictum of Newton, " Hypoth- 
eses non fingo," let us start with facts before we 
attempt to form any idea as to the nature and 
character of that apparently mysterious state known 
as sleep. In order to understand a highly complicated 
phenomenon it is well to study the circumstances under which 
it occurs and investigate the conditions that favor the mani- 
festation of the state. Now in studying the conditions of 
normal and abnormal suggestibility, I pointed out in my 
"Psychology of Suggestion" that the following conditions 
are requisite to bring about those peculiar subconscious or 
subwaking states which form the soil favorable for the 
growth and development of implanted suggestions. 

Conditions of 
Normal Suggestibility Abnormal Suggestibility 



i) Fixation of attention 

2) Distraction of attention 

3) Monotony 

4) Limitation of voluntary 

movements 

5) Limitation of conscious- 

ness 

6) Inhibition 

7) Immediate execution of 

the suggestion 



1) Fixation of attention 

2) 

3) Monotony 

4) Limitation of voluntary 

movements 

5) Limitation of conscious- 

ness 

6) Inhibition 

7) 



10 An Experimental Study of Sleep 

I have further pointed out that what we really bring 
about under such conditions is a dissociation of conscious- 
ness. In the normal waking state the dissociation is tran- 
sient, fleeting, disappearing at the very moment of its 
appearance, while in abnormal suggestibility the states are 
more or less permanent. In other words, the waking state 
tends to disappear under the conditions mentioned above. 
Now to induce sleep the first requirement is the displacement 
of the waking state. It is evident that the conditions that 
favor the suppression of the waking state would also favor 
sleep-states. As a matter of fact I have often observed in my 
patients and subjects that the conditions by which I intended 
to bring about a subconscious state in general and a hypnotic 
state in particular have often resulted in ordinary sleep. 
I have found quite frequently that the close observation of the 
conditions of monotony, limitation of the voluntary move- 
ments, limitation of the field of consciousness and of in- 
hibition, brought about not a hypnotic state, but ordinary 
sleep. I began to experiment on myself and found that I 
could put myself almost at any time into a state of deep 
sleep by closing my eyes and keeping perfectly still, dismissing 
all ideas from my mind — closing shop, so to say. I was 
able to put myself into a quiet, prolonged and often very 
refreshing sleep. I have further succeeded in the treatment 
of many cases of insomnia, by following the same lines in 
bringing about good therapeutic results. 

After many years of experimentation and observation 
I have come to the conclusion that this could not possibly 
be an accidental matter, but that there must be some close 
interrelation between sleep-states and the conditions of 
normal and abnormal suggestibility. In other words, 
the conviction was almost forced on my mind by the facts 
that the conditions I found requisite for the induction of 
dissociated states and for normal and abnormal suggestibility 
in general play also an important role in the induction of 
sleep. 

There is one fact that is specially worth while noticing 
in the process of falling asleep, and that is, the circumstance 
that we do not tumble into it in spite of ourselves, that we 
go about it in a deliberate, may be cold-blooded fashion. 



An Experimental Study of Sleep 



II 



We have to make up our minds and decide whether or no 
we want to go to sleep, or whether it is best for us to be 
asleep; and when we decide in the affirmative, we undress 
and go to sleep. The whole affair is not the after-effect of 
some narcotic, toxic, autotoxic bodies, nor the result of some 
involuntary automatic mechanism, — it is a voluntary act, — 
the result of decision. In this respect sleep is very similar 
to the abnormal state of suggestibility in which subjects can 
be artificially put. The state of abnormal suggestibility, 
the hypnotic state, is not induced by accumulation of toxic 
products in the system. The state can be brought about 
at will under the conditions described above. It is a purely 
voluntary affair, requiring the cooperation of the subject's 
and the experimenter's attention, active and steady. In 
fact, subjects whose attention is poor, — imbeciles, idiots, 
insane persons or persons whose attention is constantly wan- 
dering and fluctuating, are extremely difficult to hypnotize. 
These significant facts so often overlooked by writers on the 
subject, force on one the conclusion that the psychic factor 
is of the utmost importance in the formation of sleep-states. 
If we now scrutinize the conditions under which drowsi- 
ness and sleep occur, we find that they differ in some very 
important points from those requisite in the induction of 
hypnotic states. In the bringing about of hypnosis the 
most favorable condition is the fixation of the attention on 
some object, perceptual or ideational. So much is this 
condition of fixation of importance that some writers describe 
the nature of the subconscious by this one condition of the 
attention, and characterize the hypnotic state, not without 
some show of plausibility, as a cramp of the attention. 
Such a sweeping statement is not entirely true to fact, but 
it is true that fixation of the attention, steady and persistent, 
without flinching, constitutes a very important factor in the 
induction of the hypnotic state. In sleep, however, we 
observe that the condition is somewhat modified, — it is not 
fixation of the attention that is conducive to sleep; in fact, 
fixation of the attention is more favorable to insomnia or to 
the prolongation of the waking state. What is requisite 
is a relaxation of the attention. If fixation of the attention 
is present at all, it is only present in so far as it is requisite 



12 An Experimental Study of Sleep 

to have the attention relaxed, which under some conditions 
requires either an effort of the will or the presence of 
specially favorable circumstances. It is the will to give 
up all active relations, sensory and motor, with the external 
environment. In hypnosis there is present at first a strained 
state of attention; in the induction of sleep the strain is 
practically reduced to its minimum. In the formation of 
sleep-states all active desire must cease. That is why 
people with intense, active desires and emotions find it so 
difficult to fall asleep. On the other hand such intense 
desires and strong emotional states may, if taken advantage 
of at a favorable moment, become the best condition for 
bringing about states of suggestibility, hypnosis and all 
forms of dissociation. In fact, in this respect we may say 
that the sleep-states differ fundamentally from hypnotic 
states. Suggestibility, which is the characteristic trait of 
subconscious states and of hypnotic states in particular, is 
absent in sleep-states. While hypnosis and allied states are 
characterized by a greater facility of reactions to external 
stimulations, the sleep-states on the contrary are characterized 
by an almost complete suppression of the more complex 
reactions associated with mental processes. In other words, 
in hypnosis and allied states there is a suppression or inhibition 
of the inhibitions present in waking life; in sleep, on the 
contrary, the inhibitions are intensified. If put in terms of 
the threshold theory advanced in my work, "Multiple 
Personality," we may say that in hypnosis and allied states 
the thresholds are lowered, while in sleep states the thresholds 
are raised. 

If we turn once more to the conditions of sleep, we find 
that limitation of the field of consciousness and limitation 
of voluntary movements play a very important role in the 
bringing about of sleep-states. In this respect Huebel's 
shrewd observation is correct, — the cutting off of all external 
stimulations tends to bring about a languid condition akin 
to sleep. Prisoners in solitary confinement, unless they 
find a source of mental activity by getting some external 
stimulations to awaken their mental life, have a tendency to 
sleepiness. Where attention is relaxed, or the interest in 
external impressions is gone, there drowsiness supervenes. 



An Experimental Study of Sleep 13 

In the limitation of voluntary movements a mass of muscular 
sensations as well as kinaesthetic sensations is kept from 
pouring into consciousness, the result is a lowering of mental 
activity, a rise of thresholds characteristic of sleep. The 
cutting off of external impressions is also of importance in 
hypnosis, as when the subject is asked to keep very quiet 
and make his mind a "blank." Where there is a predis- 
position to states of dissociation the result of limitation is 
not sleep but hypnosis, with a fall of thresholds. 

The most important and possibly fundamental con- 
dition common to sleep and subconscious states is that of 
monotony. In order to fall asleep we must dismiss all our 
interests, all our thoughts. Similarly, to induce hypnosis 
we tell the subject to try not to think of anything. We 
impoverish, we make monotonous, his mental life by making 
him think of "nothing in particular." 

The fact that people may fall asleep even under intense 
stimulations is often adduced as a strong objection to the 
view that diminution of sensory stimulations is conducive 
to sleep. Thus Richet refers to the fact of "falling asleep 
at the opera, in spite of the light and the noise." This 
objection is valid only if we leave out of account the im- 
portance of the factor of monotony. It is not so much the 
diminution of the intensity of stimulations which is of 
importance in the production of sleep, as the total mass of 
impressions. In fact, it is not so much the total volume as 
the progressive, ceaseless variability of the incoming im- 
pressions that counts in the keeping up of the restless activity 
of consciousness in its adjustment to the external conditions 
of the environment. Given a prolonged stimulation or 
a series of stimulations of the same intensity, consciousness 
becomes dulled and sleep ensues. In fact, the more intense 
the monotonous stimulations are, the deeper is the state 
of sleep. 

It is interesting to note that under such conditions the 
intensity of the series of monotonous stimulations tends to 
keep up the sleep-state. With the cessation of the monoto- 
nous stimulations the sleep-state tends to disappear. The 
miller falls asleep under the continuous uniform noise of his 
mill, and wakes with the cessation of the noise. In 



14 An Experimental Study of Sleep 

listening to lecturers in a medical school I found how easily 
the monotonous, uninteresting delivery put me into a drowsy 
state, and how I came back to myself with a start when the 
lecturer stopped. Inquiring among the students, I found 
that their experiences were quite similar to my own; they 
were kept in a semi-drowsy state by the long-drawn-out 
sentences, and kept awake by the lecturer's resting-places. 
Many people who are used {o the long, continuous hum of 
a large city such as New York, for instance, find it difficult 
to fall asleep in a quiet place. 

Chapter IV 

Intermediary States 

IN many cases where it is requisite to find the causation 
of the mental trouble, and hypnotization is not 
possible, I have for many years employed a method 
which has been giving excellent results, both theo- 
retical and practical. By means of this method, which I 
have termed hypnoidization, I have been able to induce 
states closely allied to sleeping states on the one hand, and 
to hypnosis on the other. This work may be regarded as 
established, having since been confirmed by many other 
investigators, as well as by my assistants and collaborators 
in my laboratory. 

Basing myself on the conditions which I have elsewhere 
described for the induction of states of normal and abnormal 
suggestibility, as well as for the bringing about of dissociated 
states in general, I have applied the same or similar con- 
ditions in cases where hypnosis was not possible. The 
result was the induction of peculiar states which I termed 
hypnoidal. The hyp/ioidal state is of an intermediary 
character, intermediary between the waking state on the 
one hand, sleep and hypnosis on the other. Here specially 
lies our present interest in these peculiar states. The patient 
or the subject while in this state hovers between hypnosis 
and sleep. Now he may be in a condition which can only 
be characterized as light hypnosis, and then again to one's 
surprise the person is found to be in his normal waking 
state. The state evidently is highly unstable. 



An Experimental Study of Sleep 1 5 

The oscillations of the different states may be followed 
by variations in respiration. Thus the respiration is some- 
what unequal in the waking state, becomes quietened and 
more uniform in hypnosis. When, again, in the hypnoidal 
state the respiration is slow and with little or almost no 
variations, it becomes disturbed when the patient passes into 
waking state, and becomes uniform when he passes into 
hvpnosis or sleep. 

The method of hypnoidization shows clearly how the 
conditions of normal and abnormal suggestibility are utilized 
and modified in the induction of hypnoidal or intermediary 
states. I say modified, because it is just on such slight 
modifications and variations of the conditions mentioned 
above that the whole matter of hypnoidal states hinges. 
A quotation from a previous work of mine giving a short 
description of the methods of hypnoidization and of the 
character of the hypnoidal state will be opportune here. 
" The patient is asked to close his eyes and keep as quiet as 
possible, without however making any special effort to put 
himself in such a state. He is then asked to attend to some 
stimulus, such as reading or singing, or to the monotonous 
beats of a metronome. When the reading is over, the pa- 
tient with his eyes shut is asked to repeat it and tell what 
comes into his mind during the reading, or during the repeti- 
tion, or immediately after. This should be carried out in a 
very quiet place, and the room, if possible, should be dark- 
ened so as not to disturb the patient and thus bring him out of 
the state in which he has been put. As modifications of the 
same method, — the patient or subject is asked to fixate his 
attention on some object, while at the same time listening 
to the beats of a metronome; the patient's eyes are then 
closed, he is to keep very quiet, while the metronome or 
some other monotonous stimulus is continued. After some 
time, when the patient's respirations and pulse are found 
somewhat lowered, he is asked to concentrate his attention 
on a subject closely relating to the symptoms of the malady 
or to the submerged subconscious state. In other words, 
the patient is in a hypnoidal state favorable for the emergence 
of subconscious experiences. 

" The patient again may be asked to be very quiet to 



1 6 An Experimental Study of Sleep 

move, or change position as little as possible, and is required 
to look steadily into a glass of water on a white background 
with a light shining through the contents of the glass ; 
a mechanism producing monotonous sounds is set going, 
and after a time, when the patient is observed to have 
become unusually quiet, he is asked to tell what he thinks 
in regard to his symptoms. In other cases it is sufficient 
to put the patient in a relaxed condition, have his eyes shut 
and tell him to think hard of the particular dissociated states." 

Now in working with the method of hypnoidization 
I have often observed in using it that the patient at first tries 
to concentrate his attention and seems to fall into slight 
hypnosis, but pretty soon he is fully awake. In closely 
watching this condition I found that at first the patient 
attempted to fixate his attention, then lost control over it. 
His attention being relaxed he fell into a sleep-state, out of 
which he emerged again, owing to the partial presence of 
the idea of the necessity of concentration of the attention, 
as well as to the partial watchfulness present. It is this 
alternate and incomplete relaxation and concentration of 
the attention that keeps the patient on the borderland of 
wakefulness, hypnosis and sleep. In some cases the 
hypnoidal state passed into hypnosis. Thus in one of mv 
cases, V. F., at first I obtained only hypnoidal states, but 
after some time the hypnotic state gained ground and the 
subject passed into typical hypnosis and finally into a som- 
nambulistic state. In other cases I have observed that 
preliminary to the passing into the hypnotic state proper 
a short interval is present which may be regarded as a hyp- 
noidal condition. In many other cases the patient is not in 
the hypnotic condition, but still there are phenomena 
present which remind one strongly of the hypnotic state. 

The close relationship of the hypnoidal state and of 
hypnosis is sometimes forcibly brought to the mind of the 
experimenter. Some patients while in the hypnoidal state 
are observed to become unusually quiet, less talkative, 
relaxed and after a time distinctly cataleptic. The patient 
has apparently passed into hypnosis. In most of the cases 
the hypnosis is of very brief d uration. On the other hand, 
in other cases the subject falls into a sleeping state without 



An Experimental Study of Sleep 17 

as much as touching on hypnosis. The hypnoidal state is 
on the borderland of waking, sleep and hypnosis. .Sub- 
waking seems to be an appropriate descriptive term of the 
hypnoidal state. Like sleep and hypnosis, the subwaking 
hypnoidal state greatly varies as to depth and duration: 
it may range from the full waking consciousness to deep 
hypnosis. The same patient may at various times reach 
different levels, so that not all the hypnoidal states are of 
the same depth; and in that respect they are very much like 
sleep and hypnosis, which really are not always of the same 
depth. 1 

What is specially characteristic of the hypnoidal states 
is the difficulty of fixing them for any length of time, — they 
dissolve into mist as soon as an attempt is made to seize 
them, — they are extremely fleeting and evanescent. What 
specially interests us is the close relationship of the hypnoidal 
state with sleep-states. The hypnoidal state is the bridge 
that connects the waking state not only with hypnosis, but 
also with sleep. To enter sleep or hypnosis one has to pass 
through the intermediate state, the hypnoidal state. 

We may also add that this holds true not only in the 
case of passing into any of the hypnotic or sleep-states, but 
also in the case of passing out of them. A close observation 
of cases will show that in awakening from hypnosis, as well as 
from sleep, there is present a short period occupied by 
a peculiar condition of consciousness, a condition which 
is no other than the hypnoidal state. It is such states 
between sleeping and waking, whether on the way to or 
from sleep, that may be designated as subwaking, and are 
akin to hypnoidal states. 

The subwaking states are characterized by the trait of 
suggestibility. Suggestions are fully possible in such con- 
ditions. In fact, in all those cases where hypnosis is im- 
possible or impracticable the hypnoidal states can be util- 
ized for the same purpose. The subwaking or hypnoidal 
states are utilized by me and by many other investigators in 
a systematic and methodical way for the obtaining of sub- 
merged subconscious experiences. This clearly shows that 
the subwaking states, while being of the character of sleep- 
states, are also in close touch with states of dissociation. 



8 



An Experimental Study of Sleep 



One important characteristic of all subwaking states is 
the formation of hallucinations which indicate states of 
dissociation under which alone hallucinations can take place. 
On falling asleep hallucinations crowd consciousness, and on 
awakening a crowd of phantastic percepts, often giving rise 
to disconnected dreams, haunt "the halls of consciousness. " 
We may possibly term the intermediary subwaking states 
leading into sleep as hypnagogic states and the dream- 
hallucinations formed hypnagogic hallucinations; the inter- 
mediary subwaking states which arise on coming out of 
sleep we may term hypnapagogic states (from vttvos, sleep; 
and aTrayw, lead away); the dream hallucinations formed 
may be termed hypnapagogic hallucinations. In passing 
from waking states into sleep and again from sleep into 
waking, we pass through those intermediary subwaking 
states. We may graphically represent those intermediary, 
transient, subwaking states as follows : 




In other words, in going to sleep or rising out of it as 
well as in entering into hypnosis and its allied states and 
coming out of them the transitory, subwaking, hvpnoidal 
states are passed through. The subwaking states may 
therefore be regarded as truly intermediate. The subject 
in passing through the subwaking hypnoidal states may 
either fall asleep or pass into hypnosis. Facts thus clearly 
indicate that sleep-states are closely interconnected with 



An Experimental Study of Sleep 19 

intermediary subwaking states discovered in my investi- 
gation of the subconscious. In the study of sleep then we 
must devote our attention to the investigation of transitory 
subwaking states which form the transition between waking 
and sleeping. 

Chapter V 

The Induction of Sleep-States 

OWING to the kindness of Dr. Walter B. Cannon, Pro- 
fessor of Physiology at the Harvard Medical School, 
I was given the opportunity and facilities to perform 
some experiments at the Physiological Labora- 
tory of that institution. I wish to thank Dr. Cannon for all 
the kindness and consideration he has shown me in the 
carrying out of the experiments on sleep at his laboratory. 1 

Guided by the work, on account of which was given in 
the previous chapters, I undertook a series of experiments on 
the induction of sleep in different animals. I thought it 
might be well, since sleep belonged to animals as well as to 
man, to start my experiments on animal life, beginning with 
lower animals and ending with man. My experiments were 
carried out on frogs, guinea pigs, cats, dogs, infants and 
adults. It occurred to me to use the same methods to bring 
about sleep under the conditions of normal and abnormal 
suggestibility in all those various representatives of the 
ascending scale of animal life. I consequently tried to 
induce sleep under the conditions favorable for the bringing 
about of the intermediary, subwaking, hypnoidal states. 
Now I pointed out above, that the transient character of the 
subwaking hypnoidal states was due to the variability of the 
conditions under which they were induced. Hence the fact 
of oscillation or instability of such states, the subject now 
plunging into hypnosis, now into sleep, and then again 
emerging into the light of the waking state. Hence the 
mixed manifestations observed in the subjects, when in the 
hypnoidal state, now presenting the traits of hypnosis and 

1 I take here the opportunity to acknowledge my obligations to Dr. Morton Prince 
and to Dr. W. B. Cannon for the many helpful suggestions given to me in the revision 
of the manuscript. 



20 An Experimental Study of Sleep 

now of sleep. My point therefore was to induce sleep and 
its allied states, subwaking and hypnoidal, keeping as closely 
as possible to the conditions of normal and abnormal 
suggestibility. 

Now I found in my experiments on the induction of the 
intermediary hypnoidal states in man that the conditions 
of monotony, limitation of the voluntary movements, limi- 
tation of the field of consciousness were of the utmost 
consequence. In my present experiments on animals I 
followed the same line of work and as far as possible repro- 
duced the same conditions. I tried to limit the incoming 
sensory impressions, to limit the voluntary movements and 
thus produce a monotonous state by the continuous inhibition 
of new and varied stimulations. After narrowing down the 
animal's psychophysiological activity I invariably found that 
when I succeeded in maintaining closely the same conditions 
which had been found favorable in human subjects for the 
induction of subwaking states, the animal uniformly fell 
into a passive condition closely analogous to the subwaking 
state and in many instances into a deep sleep. The condition 
of the animal was often strikingly similar to the one observed 
in the human subject. The respirations and pulse were 
lowered, while mental activity in the higher animals, alert- 
ness of sensory and motor reactions to external stimulations 
in the lower animals became greatly reduced and even 
completely suppressed. In the higher animals, such as dogs, 
a transitory cataleptic state, a state in which the voluntary 
muscles retained the position given to them, could be 
observed accompanied by a disturbance of respiration and 
heart beat. The slight disturbance then subsided and 
calmness supervened. The calm lasted but for a brief 
period of time and the disturbances reappeared. The 
latter were once more succeeded by calm which ended by 
full waking state or by a deep sleep. In other words, the 
experiments, the details of which are adduced further on, 
allow me to draw the conclusion that I had here the typical 
manifestations observed under the same conditions in my 
human subjects. \ found here the manifestations charac- 
teristic of the intermediary hypnoidal states, the animal 
now passing into waking and now falling into sleep. 



An Experimental Study of Sleep 21 

Of course, in the case of the frogs the interpretation of 
the manifestations is rather uncertain. Still even in the 
frogs as the course of the experiments advanced the results 
stood out more clear and distinct, especially when viewed 
in the light of the experiments performed on the higher 
animals. 

Chapter VI 

Experiments on Frogs 

IT is probably best to begin with the facts and give 
their interpretation afterwards. It seems advisable 
to give the reader a clear and full account of my 
work as a whole, to avoid being entangled in 
a mesh of unnecessary details. While I experimented on 
a great number of frogs I present here but a few typical 
experiments. The reader will thus be in a far better 
position to get a fair view of the work and be more enabled to 
judge critically the conclusions drawn from the experiments. 
When the frog is put on its back, its lower lid (its only 
eyelid) is drawn up. If kept in the same position for a few 
minutes, the frog ceases to struggle and becomes quiet. 
The lower lid is kept shut, but when the lid is drawn down 
the frog becomes lively. If the frog is put on its back and 
stroked gently, the eyes close, the lower lid being pulled up. 
The frog becomes very quiet, but soon becomes again lively. 
The. frog was kept on its back for a few minutes; it was 
held down and its voluntary movements were restricted; 
it soon became cataleptic. There was a change in the 
respiration as shown by pneumographic tracings. 

A cloth was wrapped round the frog's head. The frog 
remained very quiet apparently in a very deep "sleep." 
The eyelids were found drawn up. The same experiments 
were repeated on other frogs, small and large, and the same 
results were obtained. 

When a cloth is put on the eyes of the frog so as to 
exclude all light, the frog sinks into a state of rest. It is 
cataleptic and can then be put in any unnatural position; 
it does not make any attempt to change its position. The 
frog reacts but feebly to sensory stimuli; the eyelids are 
found to be drawn up. 



22 An Experimental Study of Sleep 

The experiments were then somewhat modified, — 
the eyelids of the frog were held together with collodion 
painted over them. At first the frog struggled and was very 
restless, but soon it became very quiet, apparently sunk 
into deep "sleep." 

The more often the frog is put in that apparent "sleep" 
or rest-state the easier it is afterwards to induce the same 
condition. 

A big lively frog was blinded. It was easily put in any 
position, though it would not have retained such awkward 
postures in its normal healthy state, before it was deprived 
of sight. It may be well to add that the experiments were 
performed after the frog recovered from the shock of the oper- 
ation. The blinded frog could be manipulated far more 
easily than any other specimen of its kind. It could be 
placed in any awkward position and would remain so 
indefinitely until disturbed. No frog with its eyesight 
unimpaired would have remained for a moment in such 
awkward uncomfortable positions. The frog, for instance, 
was hung up by its front limbs on a board, it remained in 
the same position until disturbed. The frog was put over 
the edge of a jar where it hung with the front limbs, the 
body and hind legs relaxed in the jar. It remained in this 
uncomfortable position until disturbed. 

The blinded frog was left in the jar for a few days and 
then the same experiments were repeated with the same 
results. The frog was turned on its back, it remained in 
the same position, as if frozen and turned to stone. The 
flame of a match was applied to him and he responded to 
the pain stimuli very sluggishly, but did not turn over. 
The respiratory and swallowing movements were reduced 
from 60 to 48 per minute. If left undisturbed, he would 
remain in the same position indefinitely. 

The frog was put in a jar; he tried to jump out of it, — 
body and forelimbs were outside the jar, but the hind legs 
remained in the jar dangling. He remained in this position 
without any change. It seemed as if he fell "asleep" and 
"forgot" about the jumping out; it reminded one of the 
story of the sleeping kingdom. 

To control the experiments on the blinded frog I took 



An Experimental Study of Sleep 23 

a healthy frog which was not operated and closed its eyes 
firmly. It was put in a very awkward position. It remained 
hanging over the board without any movement for a period 
of 5 minutes. Respirations became very slow. In this 
position I could carry it round the laboratory without 
disturbing it in the least. After 5 minutes it opened its 
eyes slowly and changed its position. 

The blinded frog was put in an upward sitting posture. 
Its back was supported by a board so that it should not 
tumble over. In this attitude it remained without change 
for a long time. 

A healthy, not blinded frog, was then taken and after 
having closed its eyes firmly with my fingers for a period 
of a few minutes it was put in a sitting posture similar to 
the one given to the blinded frog. The healthy frog re- 
mained, as if stiffened in the same position. Respiration 
fell to 48 per minute. During the whole period of the 
experiment the respiration and heart beats were greatly 
reduced. Response to sensory stimuli was very sluggish; 
the limbs were in a state of relaxation. 

After a few weeks the blind frog was still alive and 
kicking. It kept very quiet and could easily be put into 
a cataleptic state. 

The blind frog remained in the same position, when 
left to itself. It remained in any posture given to it. When 
put over the edge of the jar, it remained in the same position 
without changing a single muscle. During this time it 
reacted very sluggishly to external stimulations. Respi- 
ration and heart beats were very much retarded. 

Similar experiments were carried out by me on a num- 
ber of frogs with the same results. In some cases interesting 
effects of inhibition could be observed. Thus in one of the 
actively respiring frogs with pronounced swallowing move- 
ments the latter ceased, when the muscles of the hind legs 
were seized and sharply and violently pressed or pinched. 

Frogs were placed on their backs and then a heavy 
weight was put on them to hold them for a few minutes in 
the same position. The frogs soon fell into a cataleptic 
state and remained in that state even when the pressure 
was removed. The lower eyelids were found drawn up, 



24 An Experimental Study of Sleep 

the eyes were partly closed. Some of the frogs when 
released from the pressure, relaxed their extremities and 
remained in a quiet state. 

Similar experiments I carried out on a number of frogs; 
the results were of the same character. It is interesting to 
observe that when the frogs open the eyes and turn to their 
usual position they remain for some time very quiet. 

There is one point to which I want to draw special 
attention and that is the significant fact that when the frogs 
are put in the cataleptic condition, and are from time to 
time restrained from righting themselves to their normal 
position, they finally fall into a very quiet state, — the limbs 
are relaxed and remain in a relaxed condition, the respiration 
and heart beat are greatly reduced and there is little response 
to external stimulations to which, though of slight intensity, 
they would have responded in their normal "waking" state 
by jumping away. In this respect I can fully confirm 
Huebel who pointed out this fact in his excellent work on 
the frog. 

When I carried out the above experiments on the frog, 
I was unacquainted with Huebel's remarkable work. I 
was glad on reading that observer's experiments to find that 
the work done by me did not stand by itself, but that I had 
struck a path which had been trodden by a previous explorer 
having a similar goal in view. Now when I began my 
experiments on frogs I hesitated to speak of "sleep" in frogs. 
When however I continued my experiments, I could not help 
coming to the conclusion that there are such states as sleep 
in frogs and that those states can be induced under conditions 
very similar to those we had found in human beings. Still I 
greatly hesitated to term the states induced in frogs " sleep ;" 
I termed them "rest-states." I had however a lurking 
suspicion that they might really be of the nature of sleep- 
states found in human subjects. I was therefore glad to 
find that Huebel had fearlessly and unhesitatingly described 
those rest-states by the term we describe similar states in 
human beings, — namely, sleep. I then took courage and 
walked with less hesitation and with more confidence on 
a path that had been unfortunately left untrodden and 
neglected by the foot of the scientific explorer. 



An Experimental Study of Sleep 25 

I must, however, add that I am not quite so sure as 
Huebel is that the "rest-states," induced in the frog and 
described in my experiments, are sleep-states, but I do think 
that they are closely analogous to what we regard as sleep- 
states in the higher animals. 

Without knowing of Huebers work I came pretty nearly 
to the same results. I observed as Huebel had before me 
that frogs after they had been put in the characteristic cata- 
leptic condition described by investigators, such as Czermak, 
Preyer, Danilewsky and others, that the frog passed into 
a quiet state, the limbs, though keeping apparently the same 
position, really not being any longer cataleptic, but rather 
relaxed, that the respiration and heart beats were greatly 
lowered and that if the frog could be left in this state without 
any disturbance, it would remain in that quiet condition for 
a very long time. 

I did not observe as Huebel did that the frogs put in 
such states remained in it for over five hours, but I did observe 
that if the environment and external stimulations could be 
kept quiet, the frogs would remain in their passive states 
for a very long time. Unfortunately, the place where I 
worked was rather noisy; in fact unusually so, for the success- 
ful carrying out of such delicate experiments. I should not 
wonder then that I could not fully get all the results that 
Heubel got who was working under more favorable con- 
ditions. I am not quite ready to claim that the passive 
states in which the frogs fall are really sleep-states, a claim 
defended very strongly by Heubel, but I do favor Heubel's 
statement and think that the states of the frog, after the 
cataleptic state has passed, is very much like what is usually 
regarded in the higher animals as sleep. 

Now if we scrutinize more closely the series of experi- 
ments carried out on the frogs, we find present the conditions 
of monotony and of limitation of voluntary movements as 
well as of limitation of what may be regarded in the frog as 
consciousness, or of the limitation of the activity of the 
sensorium by cutting off the regularly incoming sensory 
stimulations. As a result we find something analogous to 
what we should have expected in the human subject under 
like conditions, namely, the presence of peculiar passive 



26 An Experimental Study of Sleep 

states, — that is all that we are thus far justified to say of 
them, observed and described as they are by experimenters 
who do not have the possibility of getting the subjective 
experience of the animal under observation. 

What we find in the state of the frog is a condition 
somewhat analogous to what we have found in our experi- 
ments in human subjects, namely the presence of intermediary 
states of the subwaking or hypnoidal type. The symptoms 
observed differ somewhat, but in general they may be regared 
as alike. We find a passive state with cataleptic mani- 
festations. The state varies from catalepsy to relaxation 
or what may be regarded as lethargy, and again from 
passivity to activity, from sluggish to very lively reactions 
in response to external stimulations. We have therefore 
here, manifestations which remind one of like manifestations 
in the human subject, namely subwaking, hypnoidal states 
which are on the borderland of waking, hypnosis and sleep. 
Of course, we should not expect to find that frogs which 
stand so low in the scale of vertebrates would manifest 
phenomena of the same character as the higher vertebrates, 
but we should expect that some similar phenomena, though 
otherwise widely different, would be present. This is pre- 
cisely what we find in the frog. We find the general 
characteristics, though rather vague, of what is after- 
wards fully developed in man as the subwaking, hypnoidal 
state. 

We must remember besides that the hypnoidal state 
is very unstable and its manifestations, having the charac- 
teristics of waking-state, sleep and hypnosis, greatly vary in 
different individuals and at different times in the same 
individual. We should therefore expect that the hypnoidal 
state would show still more radical differences from the 
typical in the various species of animals, especially in those 
that stand so fa-r apart from each other as frog and man. 
What is surprising to me is not the fact of the variation and 
great difference of the hypnoidal state in the frog as con- 
trasted with man, but that the difference is really not far 
greater, considering the gap that exists between the two 
organisms. In fact, the similarity is far more striking than 
is the difference between the hypnoidal states of the two 



An Experimental Study of Sleep 27 

contrasted organizations so widely apart in the scale of 
evolution. 

Mv view then is that the phenomena observed in the frog 
are hypnoidal in character. The phenomena themselves 
as well as the conditions under which they are induced 
warrant my view of the hypnoidal nature of the states. 

In this respect we can well understand the apparent 
disagreement of the early observers on the subject. Czermak 
and Danilewsky regard the phenomena as being of the 
hypnotic order, Heubel regards them as being more of sleep- 
states, while Preyer views them as being the results of fright 
which give in the waking-state cataleptic manifestations 
closely similar to those observed in hypnosis. Verworn 
who regards the phenomena as "Lagecorrectionen" due 
to central inhibitions really does not conflict with any of 
the views. It is simply a general physiological hypothesis 
which may be in accord with any view, a physiological 
hypothesis which may or may not be true; it is a hypothesis 
far removed from the special facts and should be tested on 
its own merits. My point of view is not a matter of hypoth- 
esis, but describes and explains the phenomena in terms of 
states having similar manifestations and produced under 
the same conditions, states which are more developed and 
stand out more pronounced in higher animals. These 
states possess many of the characteristics of the waking 
state, sleep and hypnosis. Hence the reason why the early 
observers regarded the phenomena as waking states, as 
Preyer did; others regarded them as hypnosis, a view 
maintained by Czermak, Heidenhein, Danilewsky; while 
other investigators regarded the phenomena as sleep-states. 
As a matter of fact the phenomena and the conditions under 
which they are induced make the view highly probable that 
the different investigators are not far away from the truth, 
but not being acquainted with the peculiar hypnoidal states 
described, they observed the phenomena in too one sided 
terms, in terms of sleep, or hypnosis, or of waking-states. 
In reality the phenomena and the conditions under which 
they are induced point strongly to the fact that the states are 
hypnoidal in character, states which partake at once of all 
the three apparently contradictory manifestations, — waking, 



28 An Experimental Study of Sleep 

sleep and hypnosis. Now the manifestations of the waking- 
state, and now the symptoms of sleep, and now again of 
hypnosis predominate. In short, the state induced in the 
frog under the conditions of monotony, limitation and inhi- 
bition is a variety of the subwaking, hypnoidal states. This 
induced hypnoidal state being intermediary in character 
may either partake of the catalepsy of hypnosis strongly 
modified and manifesting itself differently in the frog than 
in the human subject, or may again go over into the passive 
state of "sleep" or some state analogous to it. 

It is perhaps of importance ' to call attention to the 
significant fact that the first stages induced in the frog are 
rather of an unstable character, — the frog when put on its 
back and kept down for but a short time falls into an appar- 
ently cataleptic state of short duration. The animal soon 
rights itself and is fully awake as before. This instability 
is very characteristic. Now the hypnoidal states are just 
characterized by this fundamental trait of instability. It is 
only when the condition of monotony, limitations of 
voluntary movements and inhibition are sufficiently pro- 
longed that the catalepsy becomes more or less fixed for some 
period of time, and when this passes off, and the conditions 
under which the frog is kept are continued still further, it is 
only then that the frog sinks into a passive state which may 
last indefinitely, unless brought out of it by some strong 
stimulation. It seems to me then, that if we take all this 
into consideration, we cannot possibly describe the state in 
which the frog is put in other terms than what we have on 
other occasions discovered to be the intermediary, sub- 
waking, hypnoidal state. 



Chapter VII 

» 

Experiments on Guinea-Pigs 

WITHOUT going into physiological speculations 
let us once more return to our facts. 
In the pathological Institute of the New 
York State hospitals, I had occasion to carry on 
a few experiments on guinea-pigs. One of the guinea-pigs 
was put into a cataleptic condition by gentle stroking, 
while another was put into a similar state by simply seizing 
him suddenly. The guinea-pigs lost the control of their 
extremities and could not move even when stimulated by 
strong electric currents. After a few minutes left in the 
same position the guinea-pigs recovered the use of their 
extremities. The holding down of the animal to one 
position of the limbs, the gentle stroking, or the strong 
emotion of fear favored the condition of monotony and 
inhibition. In my present experiments I tried something 
similar, namely, to put the guinea-pig under the same 
conditions of experimentation under which I put the frogs 
and my human subjects. 

A guinea-pig was bound with straps and plaster strips 
and was left in this condition over night. In the morning 
he was found in the same place, — he could not free him- 
self. He was very much weakened and paralyzed. He 
did not struggle much and could easily be put into a passive 
state. Unfortunately it was hard to say whether the passive 
state was due to his weakness or to the conditions under 
which he was artificially put. 

Young guinea-pig, of a few days old; very lively. I 
took him in my hands and kept him quietly and then put 
a blind on his eyes as I did in the case of the frogs. At 
first he struggled, then became very quiet. Respiration 
fell from 120 to 90 per minute. He remained in the same 
posture for about 35 minutes. He did not respond to 
stimuli such as intense noises. After fifteen minutes 
respiration was regular and fell to 60 per minute. The 
guinea-pig looked like a ball of immovable matter, — the 

29 



30 An Experimental Study of Sleep 

only thing indicating life was the regularity of the respira- 
tions. After a few minutes I found that he started at intense 
stimuli, but still did not change posture. As he was near 
the end of the board his foot slipped from relaxation of the 
limbs, he changed posture, but remained immovable. 
After half an hour he began to stir and move his head 
slightly. 

On closing the pig's eyes there was a difference in 
respiration, — the respiration fell and became more uniform. 

I tried now to modify somewhat the experiments. I 
found that the pigs were extraordinarily lively animals and 
struggled a good deal. Now in my experiments on human 
beings where there was too much opposition to the induction 
of subwaking states, I could reduce the opposition by the 
use of hypnotics and anaesthetics. I tried similar experi- 
ments on my frogs, but the results were not satisfactory. 
The anaesthetized frogs either reacted very much like 
normal animals, or when given a somewhat larger and more 
effective dose soon died. I attempted to paint the skin of 
the frog with collodion to exclude stimulations of the skin, 
but the frogs died in convulsions. When I soaked their 
skin in chloroform or ether I had the same results. Evidently 
the skin of the frog absorbed the chloroform or ether and 
produced undesirable poisonous effects. Since however I 
did have success with my human subjects under similar 
conditions, I thought I might have some favorable result 
in the case of the guinea-pigs. 

A guinea-pig was put under chloroform for a few 
seconds. Respiration fell to 48 per minute. Reflex 
movements were well preserved. Eyes were partly closed. 
The guinea-pig started every time, but did not react to sound 
or light-stimuli, and very sluggishly reacted to pain-stimuli. 
He shivered and then closed his eyes. About 15 minutes 
later he began to react to stimuli. The reactions conformed 
to Pfliiger's law 1 .- Stimulations called forth reactions on the 
same side. About half an hour later the pig began to feel 
pain, cried on sharp pinching of the front paw. Respiration 
was still greatly reduced. By closing his eyes and by 
continuous gentle stroking of his back, it was easy to make 

1 See p. 87, footnote. 



An Experimental Study of Sleep 31 

him fall asleep. He rolled up in a ball and seemed to sleep 
quite comfortably. 

Guinea-pig under ether for about a minute. Respi- 
ration and heart-beat greatly lowered. Muscles were 
relaxed; eyes were half closed in sleep. Later on he awoke 
and was fully alive to external stimulations, though not so 
lively as usual. I put him in my hand, kept him very quiet 
and closed his eyes. He evidently fell asleep as he did not 
open his eyes when I removed my hand from them; on 
the whole the pig kept unusually quiet without stirring 
a muscle. 

A guinea-pig was put under ether for 30 seconds. 
Reflex of wiping with forepaws was present. Reactions 
to stimuli were rather sluggish. After a few minutes the 
pig awoke, but had a tendency to go to sleep again when I 
put him in my hand, kept him very quiet and closed his 
eyes. He fell into a quiet sleep, his muscles relaxed; 
respiration and heart-beat were much lowered. When 
disturbed, he became fully awake and began to eat, but went 
immediately to sleep again, when put in my hand and kept 
quiet. Now and then a passing state of resistance of limbs 
was observed. The limbs once changed often retained 
the posture given them. This state however was far from 
being as marked as it was found in the case of the frog. 

When light was excluded from one of the eyes of the 
animal the other eye began to contract and close; the animal 
became unusually quiet. Anything that excluded visual 
sensory stimuli and brought about limitation of the voluntary 
activity of the pig produced a state very much akin to sleep 
with now and then a slight catalepsy quickly followed by 
relaxation of the limbs. 

A guinea-pig was fixed on a board, — he kicked violently. 
Collodion was used to fasten his eyelids together and as 
in the case of the frog, he became quiet and ceased to make 
attempts at fighting. 

A guinea-pig breathed chloroform for two seconds 
only. It seemed to have affected the animal sufficiently 
to make him quiet. He did not fight; lost a good deal of 
his liveliness. I put my hand on him, restricting his move- 
ments. He did not resist; I then closed his eyes; he remained 
without stirring in the same posture. 



32 An Experimental Study of Sleep 

When I closed one eye of the animal, the other closed 
also and the animal seemed to have gone to sleep, the limbs 
being in a relaxed condition. 

After some time he opened his eyes again; chewing 
movements were present; active, lively and restless, sniffing 
about in all directions. I once more took him in my hand, 
kept him very quietly, but firmly, — his activity subsided, he 
ceased to struggle, eyes became contracted as well as pupils; 
finally eyes closed very slowly. The animal sank into 
a state of torpitude. Respiration and heart-beat fell. 

Thus far we may say that the experiments on guinea- 
pigs gave results somewhat similar to those of the frogs, 
though the cataleptic states were not so pronounced, — in 
fact they were very transient. Still the induction of sleep 
was brought about under conditions of monotony, limitation 
and inhibition. It was far more difficult to bring about rest 
or passive states in guinea-pigs than in frogs, on account 
of the great liveliness and ceaseless activity of the pigs. 
It may be objected that the anaesthetics somewhat modified 
the result, because it might be claimed that the sleep-states 
induced were really due to the anaesthetics used. This 
objection however can be easily obviated by the rejoinder 
that the action of the anaesthetic was only to reduce the 
extraordinary activity and restlessness of the animal and 
thus make it easier to induce sleep. The sleep-states 
themselves were really produced under the same conditions 
as were the ones induced in frogs and in my subjects. In 
fact even when the guinea-pigs were really lively and active 
it was sufficient to subject them to the conditions described, 
when they gradually fell into a state very much of the 
character of hypnoidal states and sleep. The phenomena 
though were not so well marked as in the frogs. 



Chapter VIII 

Experiments on Cats 

IN passing now to my experiments on higher animals 
the results seem more striking and convincing. As 
in the case of the frogs, I can only quote some of the 
experiments performed, it would take up too much 
space of the present paper to quote all of them. Besides 
little will be gained by a literal transcription of my note- 
book, since many of the experiments are simply repetitions of 
one another. I shall bring as many facts before the reader 
as will sufficiently introduce him to the work and make him 
so familiar with the experiments performed that he may be 
enabled to follow closely the various threads that go to form 
the main strength of the present research. 

A young kitten of about six weeks, very lively, runs about 
playfully, wide awake. When put on its back, it struggled 
violently. I then put the kitten in a cloth, kept it firmly so 
as to limit all the struggles and voluntary movements. At 
first it struggled and fought, but I restrained the kitten as 
much as possible, and then I closed its eyes for about a 
minute. The struggles ceased gradually and the kitten 
passed into a passive state of sleep. When I relaxed my 
grip on its body, it remained in the same position without 
moving a limb. At first the respirations went up and also 
the heart-beats. But as the kitten became more passive 
and went into deep sleep, the respirations and heart-beat 
fell. The kitten was deeply asleep, did not react to sound 
stimuli or to light ; eyelids were firmly closed. At first a 
slight resistance in the outstretched paws, strongly suggestive 
of hypnotic catalepsy, was observed, soon the paws were 
fully relaxed and easily changed to any position, but without 
retention of impressed posture. The sleep lasted for more 
than twenty minutes and would have lasted longer, had it 
not been for the fact that I disturbed the kitten's repose to 
continue my experimental work. 

The same experiments were repeated again and again 
under the same conditions of monotony, limitation of volun- 

33 



34 An Experimental Study of Sleep 

tary movements and inhibition. The results were uni- 
formly the same. It may be well to call the reader's atten- 
tion to the fact that holding the kitten down firmly, thus 
limiting its voluntary activity, is really at the same time 
conducive to greater monotony of peripheral sensations 
coming from the action and movements of the muscles, 
joints, synovial surfaces and so on; so that the factor of 
limitation largely aids the condition of greater monotony. 
Although the pressure exercised on the animal during re- 
strictions may be intense, still, as we have pointed out, it is 
not so much the intensity of the sensory mass which keeps 
up the waking state, as the manifoldness and the volume 
of sensations and reactions ceaselessly varying from moment 
to moment as to quantity, quality and intensity. 

The kitten was restricted in its movements; it was held 
down for some time, but it did not go easily into a quiet 
state. I found that the best arrangement was to enwrap 
the extremities, the hind extremities at least, in a cloth. 
This limited the voluntary movements effectually. It was 
still easier, when all the extremities were enwrapped in a 
cloth. When now I put my fingers over the kitten's eyes 
and closed them, there was little resistance and in a few 
seconds, not more than half a minute, the little thing was 
extremely quiet and in a minute or so it was fast asleep. The 
fingers were then removed, the kitten's eyes remained firmly 
shut. In fact, the eyelids resisted all efforts to open them. 
When forcibly opened, the eyeballs were found rolled up 
and the pupils were contracted. The kitten would have 
probably kept on sleeping for some time, if judged by what 
had been observed in other kittens under similar conditions, 
had it not been disturbed in order to have the experiments 
repeated. 

The kitten was snugly put away in a cloth, and all four 
extremities were restricted from voluntary movements. At 
first the kitten struggled a little, but was soon quieted. I then 
shielded the kitten's eyes with my hands, while I held it firmly 
for a few seconds only. The kitten's eyelids became half 
closed and finally closed fully. When the extremities were 
tested immediately, they were found resistive and slightly 
cataleptic. Occasionally the resistance was quite marked. 



An Experimental Study of Sleep 35 

The cataleptic state was rather transient. In some experi- 
ments I even succeeded in raising the paws into uncomfort- 
able postures where they remained without change for a brief 
period of time. After a few seconds the catalepsy of the 
extremities passed off and the limbs were in a state of re- 
laxation. The kitten did not react to stimuli, such as sound, 
light or smell; even slight pinching, change of the extremi- 
ties, shifting of the posture of the body did not produce any 
reaction. When aroused from sleep, the kitten yawned 
and stretched its paws, looked sleepy and reacted sluggishly 
to external stimulations. 

Kitten struggled hard when put on its back. It was 
enwrapped in cloth and still kept on its back, where it was 
held firmly without being allowed to turn over or even to 
move. I then closed the kitten's eyes. After a minute it 
remained in the same position. The kitten was lying 
quietly on its back, though the position was rather unusual 
and the whole attitude was very uncomfortable. The paws 
were raised in the air and at first there were manifestations 
of resistivity about the joints, but soon the resistivitv passed 
off and the limbs, though raised, were really soft and relaxed. 
A little later the paws dropped slowly and remained in a 
state of relaxation. The catalepsy was replaced by lethargy. 
The kitten did not react to pressure or to tickling of the 
paws. When sounds were produced close to its ear, the 
ear moved, but otherwise, the posture of the kitten remained 
unchanged. Tickling of nostrils made it move its head, but 
the kitten remained in the same posture with eyes firmly shut. 

The kitten was wrapped in its cloth as usual. At 
first the kitten was greatly excited and squealed. It was 
rather more difficult to make the kitten quiet than it was 
in previous experiments. The excitement was antagonistic 
to sleep. When finally quieted, which took some time, the 
result was even more successful than on previous occasions. 
The kitten was fast asleep. Before going into the sleep- 
state the same phenomenon of transient catalepsy and re- 
sistance was quite marked. The limbs then assumed a 
relaxed condition. It slept so soundly that stimuli that 
would have awakened the kitten on previous occasions did 
not disturb it at all, but simply called forth reflex reactions. 



'36 An Experimental Study of Sleep 

The kitten slept for more than half an hour. It was then 
rudely awakened by me. The kitten was very sleepy and 
soon closed its eyes and sank once more into a deep sleep. 

Three kittens eight days old. Eyes were open. Their 
movements were still incoordinate. They resisted, when 
put upon their backs. The kittens were wrapped in a cloth 
one by one. At first they struggled violently, but after- 
wards they became quiet and fell into a deep sleep. The 
limbs were in a state of relaxation. No manifestation of 
rigidity or of catalepsy could be observed while passing into 
or coming out of sleep. The induction of sleep took some 
time, but a few repetitions made the onset of sleep easier. 

The kittens were wrapped in a cloth and their move- 
ments were restricted. After a little struggle and spitting 
they went to sleep. This time no symptoms of catalepsy 
could be observed. The kittens were probably too young 
to manifest any of these phenomena, for later the phe- 
nomena of catalepsy during the time of going into and coming 
out of sleep were, relatively speaking, quite marked. Closing 
the eyes did not play such an important role in young kittens 
as did the condition of limitation of voluntary movements. 
In this respect young kittens behave somewhat similar to 
young infants. 

Kitten, two and one half weeks old; very lively. It 
struggled to get free. After three minutes the kitten was 
put to sleep; it was wrapped in a cloth and slept peace- 
fully. On my attempt to open its eyes there was a little 
resistance, but not marked. On examination the eyeballs 
were not found rolled up, but they looked staring and 
sleepy, and the pupils were contracted. The kitten closed 
its eyes immediately after and went to sleep again. There 
was little or no response to external stimulations of sound. 
In the next room much noise was made by a carpenter 
hammering with all his force. This was not favorable to 
sleep, but the kitten was deeply asleep and remained un- 
disturbed. The kitten slept for fifteen minutes and was 
awakened by me for further experimentation. 

The cloth has proved itself an excellent factor in putting 
the animals to sleep. This may be due to the fact that the 
movements are well limited without much pressure; the 



An Experimental Study of Sleep 37 

pressure present is more evenly distributed, hence, also 
more monotonous, a circumstance which greatly helps in 
bringing about sleep. The conditions must all cooperate 
to bring about monotony. 

An attempt was made to put a kitten to sleep without 
the cloth. The animal was harder to handle, it took me 
some ten minutes before the kitten was made quiet. It 
fell asleep but for a brief period of time, possibly not more 
than a minute. Then it opened its eyes. Now for that 
short period the paws were found extended, somewhat re- 
sistive to but retentive of impressed movements. The paws 
trembled visibly. This tremor was due to the incoordina- 
tion of the motor activity of the kitten. 

I observed in my experiments on subjects and patients 
that sudden fright might bring about subwaking states and 
sometimes even hypnotic and somnambulistic states. Now 
when tested on kittens similar results were obtained. When 
the kitten happened to be specially refractory, it was fright- 
ened by sudden strong stimulations or by suddenly turning 
it around and around. To my great surprise I found that 
the kitten's struggles subsided, — the respiration became 
lowered and the kitten was asleep. As the experiments 
gave like results the few described will be sufficient for our 
purpose. 

When one of the kittens was very excited and in a fight- 
ing mood, I seized it suddenly, kept it down firmly, the animal 
became very quiet, fell into a passive state and then was 
fast asleep. 

Of three young kittens I seized one after another quite 
suddenly. The kittens became much excited. One after 
another was put in a cloth, their limbs wrapped all round 
and kept down quite firmly, so that they could not move. 
There was but little opposition and still less fighting. By 
way of intensifying the effect they were given a couple of 
good shakings, the little ones became quiet, and fell into a 
sound sleep. They did not react to sensory stimuli; their 
paws were slightly resistive at first and then relaxed. Respi- 
ration, from being labored and quick, became quiet, uniform, 
easy and lowered. 

These experiments were repeated by me over and over 



38 An Experimental Study of Sleep 

again and with the same results, showing that the latter 
were not a matter of accident. In fact I found that 
when I wanted to put the little kittens to sleep speedily, 
to frighten them by shaking was the surest way of putting 
them into a more agreeable mood and thus send them off 
without delay into a sound sleep. 

In the experiments on the kittens we find the phenomena 
of the subwaking states somewhat more developed than in 
the guinea-pigs or in the frogs. The cataleptic phenomena 
are not so pronounced as they are in the frog, but the mani- 
festations of the subwaking states approach more closely 
the manifestations observed by me in human subjects. 
The state is more hypnoidal in character, there is present 
the transient, scarcely perceptible catalepsy which appears 
for but a moment, giving way immediately either to sleep 
or to the waking state. Of course, we should not expect to 
meet with a typical, fully developed suggestibility or som- 
nambulistic state in guinea-pigs or in kittens, considering 
the fact that even in man, the imbecile, the idiot and the 
mentally obtuse hardly go into any such state. It requires a 
mind of a highly organized constitution to get into a state 
of abnormal suggestibility and of somnambulism with their 
accompanying manifestations. What, however, we do find 
is the characteristic instability of the manifestations of the 
intermediary, subwaking, hypnoidal states, having some of 
the most general somatic symptoms of hypnosis, such as 
slight catalepsy, but leading into a passive condition on 
the intensification of the state. The state in which the 
animal is plunged under the condition of monotony and 
limitation is hypnoidal leading toward sleep. 



Chapter IX 

Experiments on Dogs 

AS we come nearer to the higher animals we find it 
easier to interpret the phenomena under observa- 
tion and experimentation. The subwaking states 
become more defined and sleep is fully recognized 
at the first moment of its oncome. Thus in dogs we can 
more easily interpret the different motor activities in relation 
to their subjective correlatives and accompaniments. Man 
can so closely put himself into the subjective mood of the 
dog he knows that he can understand apparently the 
slightest expression of the animal's wishes and emotions. 
The artificial selection of the most intelligent and most de- 
voted dogs as well as the constant companionship with the 
human race could not but affect the canine races and bring 
the most manifold expression of their emotions, wishes, and 
desires within the scope of human interpretation. Dogs 
have the mental touch of man and are described by the poet 
as dreaming in their sleep : 

"Consueta domi catulorum blanda propago 
Degere, saepe levem ex oculis volucremque soporem 
Discutere, et corpus de terra corripere instant, 
Proinde quasi ignotas facies atque ora tuantur." 
Lucretius describes vividly the active dreams of the 
hound hunting in his sleep : 

"Venatumque canis in molli saepe quiete 
Jactant crura tamen sudito, vocesque repente 
Mittunt, et crebras reducunt naribus auras, 
Ut vestigia si teneant inventa ferarum: 
Experge factique sequntur inania saepe 
Cervorum simulacra, fugae quasi dedita cernant; 
Donee discussis redeant erroribus ad se." 
Dogs have some imagination, even if they are not poets, 
and cannot retort man in kind. Dogs, standing higher in 
the scale of development, lend themselves far better than the 
rest of lower animals for the study of sleep. As adult dogs 
are rather difficult to manage for sleep experiments, because 

39 



40 An Experimental Study of Sleep 

of the excitement in which they are thrown and because of 
their resistance to being handled by men other than their 
masters, I selected for my experiments young dogs, especially 
puppies. I did the same thing in the case of cats for the 
same reason, as grown-up cats are still more unmanageable 
than dogs. It is true, as Huebel has pointed out, that if the 
master of the dog should try his hand, he would no doubt 
succeed in putting the dog to sleep. Puppies are very docile, 
they get easily adapted to a new person, and do not mani- 
fest the individual liking of their master and the abhorrence 
of strangers as grown-up dogs do. I have no doubt that if 
a grown-up dog should be put by his master under the con- 
ditions of monotony, limitation and inhibition, the success 
would almost be certain in each and every case. In fact, 
I tried the experiment on an older dog of mine with great 
success every time I put the dog under the requisite condi- 
tions conducive to the oncome of subwaking states and sleep. 
I shall give an account of these experiments in this research. 
I find that dogs, like men, easily fall into subwaking states 
and sleep. 

There is also another reason why I chose puppies for 
my experiments. Puppies, especially very young ones, 
sleep a good deal and not having the nervous activity and 
distractions of older dogs are more amenable to the condi- 
tions of subwaking states and sleep. In carrying out experi- 
mental work it is best to select the material and put it under 
the most favorable conditions. 

We may pass now to the experiments proper. I quote 
from my notes those experiments which are typical of the 
rest. 

Two puppies of about two months old; very lively, 
excitable, and barking violently. After some struggle each 
one was wrapped in a cloth so that even the forepaws did 
not protrude. At first they were greatly excited by the 
proceeding and proclaimed their indignation by loud yelp- 
ing. I took my turn with each one separately. The puppy 
was held down firmly and given no chance to move its body 
or to struggle with its paws. I also closed the puppy's eyes 
with my fingers. The puppy struggled and wriggled under 
my hand, but I held on tightly. Gradually the puppy ceased 



An Experimental Study of Sleep 41 

its struggles and became very quiet. Respirations became 
slow and regular. I gradually released my grip on the 
dog, when I found that its eyes were firmly closed. The 
puppy was fast asleep. The same performance was carried 
out in the case of the other puppy. After five minutes, 
during which time I held the dog tightly and kept all the 
extremities in close grip, the puppy passed into a quiet state 
and fell asleep as the first one did. Respiration was slow 
and uniform. Both puppies slept peacefully. There was 
no response to external stimuli. Limbs were in a state of 
relaxation. In spite of the noise in the neighboring room 
the puppies kept on sleeping. After twenty minutes one of 
the puppies woke up, made some show of struggle, but the 
eyes remained shut and he fell asleep again. I tried to 
loosen the cloth in which the puppies lay enwrapped. My 
manipulations did not disturb their sleep The puppies 
kept on sleeping the sleep of the just. After a sleep of 
about an hour I had to disturb the repose of the little ones 
and wake them up, as I had to leave the laboratory, other- 
wise they might have slept much longer. 

The cloth was now uniformly adopted by me in my 
experiments for the control of the voluntary movements. 
Unless the little ones were wrapped in the cloth there was 
great difficulty to restrict their activity. The puppies fought 
like furies. One of them was specially unmanageable. A 
few shakings quieted him. The puppy was wrapped in 
a cloth and after a few minutes went into a deep sleep. It 
withdrew the paws on irritation or on pinching, but the eyes 
remained firmly shut. Respiration and pulse were slow. 

The puppies were put to sleep under the same condi- 
tions. This time they could not sleep soundly, on account 
of the continuous noise in the next room. They woke up 
every time, but fell asleep again. They growled in their 
sleep, evidently reacting to the external noises, but they did 
not wake up. One of the puppies turned on one side, 
apparently to make himself more comfortable and kept on 
sleeping. They were, however, to-day more restless than 
they were on former occasions. Maybe hunger gnawed 
at their entrails, maybe it was the noise of the school that 
the puppies could not stand. After about a quarter of an 



42 An Experimental Study of Sleep 

hour they woke up and looked like two little surly pups. I 
gathered them once more up into the folds of my cloth, and 
gently, but firmly, forced them to sleep again. They went 
to sleep much more easily with no fighting. When passing 
into sleep, I tested the forepaws of each of the puppies. As 
this time the forepaws were quite free, I could observe well 
their position, change them, and manipulate them. At 
first the limbs showed some resistance to change of retained 
position impressed on them, a slight cataleptic state. Then 
the limbs relaxed and remained in this condition till the 
end of the experiment. This time the noise in the adjoin- 
ing room ceased and the youngsters seemed no longer dis- 
turbed. I let them sleep for about three quarters of an 
hour, when I began to tickle them, pinch them slightly, and 
change the position of the paws. They began to move 
restlessly and gradually got out of sleep. The eyes opened 
lazily, and they evidently felt ready to go to sleep again. 
Before waking up fully there was a slight state of resistance 
in their forepaws, catalepsy seemed to return again. This 
slight catalepsy in regard to retained postures and to changes 
of the position of the extremities lasted a few seconds and 
disappeared. Thus in getting out of sleep the puppies passed 
once more through some subwaking state with its accom- 
panying catalepsy. 

The puppies were put to sleep again. The conditions 
of monotony and limitation were the same as before. Fore- 
paws were free, protruding from the cloth. When the pup- 
pies sank into sleep, the paws were slightly resistive. The 
least disturbance brought the puppies out of the passive 
state. Typical manifestations of subwaking, hypnoidal 
state were present. Respiration gradually fell, the 
passive state became intensified, and the puppies fell into 
a sound sleep. The paws became fully relaxed. The eye- 
lids were firmly shut and at first resisted pulling apart. 
When the eyelids were separated, the eyeballs were found 
rolled up; pupils were in state of contraction. When I let 
go the eyelids, they closed again and remained firmly shut. 
There was almost no response to external sensory stimula- 
tions. The puppies slept half an hour, when I began to 
waken them slowly, again before full waking a slight cata- 



An Experimental Study of Sleep 43 

lepsy was observed in the limbs, the puppies passed through 
the intermediary, hypnoidal state. They looked sleepy 
when they opened their eyes and kept closing them. 
They stretched their little paws as after a good sleep and 
yawned. 

One of the puppies was very irritable and surly; it 
fought like a little fury. It squealed, barked and yelped. 
After a little jostle in the cloth it fell asleep peacefully. 
Again a slight catalepsy of the limbs was observed for a 
brief period of a few seconds, then relaxation set in. The 
puppy slept very soundly; it did not react to stimuli of 
medium intensity. Reflexes of forepaws were present and 
when the stimuli became summated the paws changed posi- 
tion, the body then also tended to change its posture. The 
eyelids were firmly closed; when opened by force, the eye- 
balls were found rolled up and the pupils contracted. 

The other little puppy was more amenable to treat- 
ment, — it did not resist, but seemed to be resigned to its 
fate. When wrapped in the cloth, it was very good natured. 
When I put my fingers on its eyelids and had them firmly 
shut, the puppy remained in the same position without 
fighting. Respiration was quiet, uniform, lowered. As 
the puppy sank into sleep the paws were found slightly 
resistive to bending; they were extended, but soon became 
relaxed and remained so throughout the sleep state. The 
puppy slept quite peacefully. Reflexes of forepaws were 
present. It did not react to slight stimulations, such as 
tickling or pinching of the skin, or even to pricking of the 
forepaws. It did not react by shifting the body or by wak- 
ing up and opening the eyes, it only moved the forepaw that 
had been stimulated. The eyelids were firmly shut and 
resisted opening. When opened by force, the eyeballs were 
found rolled up, so that the whites or the sclera could be 
well seen partly covered by nictitating membrane. The 
dog was awakened by summation of slight stimulations. 

Three new puppies were very tractable. They fell 
asleep with the greatest ease imaginable. The puppies 
were about two and a half weeks old, were quite gentle and 
showed almost no resistance. The same phenomena were 
present as in the other dogs; they went to sleep under the 



44 An Experimental Study of Sleep 

same conditions, their paws for a brief period of a few sec- 
onds were extended and slightly resistive. Limbs retained 
the position given to them. The eyelids were firmly shut 
and there was resistance to attempts to force them open. 
When forced open, the eyeballs were rolled up, and the 
eyelids closed as soon as they were let go. The puppies 
seemed to possess the power of sleeping indefinitely. Now 
and then sucking and snapping movements were observed. 
They slept for more than an hour and would have gone on 
sleeping had not they been rudely shaken out of their peace- 
ful repose. 

The experiments were repeated over again with the 
same results. As the puppies got older the manifestations 
of the transient, intermediate state became more pro- 
nounced, — catalepsy was more evident on falling asleep. 
The same held true in the case of waking up. There was 
a slight stiffness and catalepsy of the paws for a brief period 
when the puppy emerged from sleep. On falling asleep the 
puppies did not tumble at once into that state, they opened 
and shut their eyes, when my fingers were released from 
pressing their eyelids. They kept on blinking the eyes. 
The lids came nearer together and finally closed. The 
same process of blinking was observed on waking; they 
seemed to wake and fall asleep again, thus being really in the 
intermediary, hypnoidal state, hovering between waking 
state and sleep, both on going to and coming out of sleep. 
With the repetition of the experiments the little fellows 
earned to go to sleep with greater and greater ease, mani- 
festing, as time went on, more and more clearly the charac- 
teristic symptoms of subwaking and sleep states. After 
a time there was no need to keep their eyelids closed with 
my fingers; it was enough to shade their eyes with my hand 
or with any opaque body and the eyes after a few seconds 
began gradually to close. A slight tremor of the eyelids 
was observed as they kept on opening and closing, somewhat 
similar to what we find in the first stages of hypnosis. Only 
here it was not really hypnosis, but the hypnoidal state, 
partaking of hypnosis, waking state and sleep. The pup- 
pies did not really go into any hypnosis, but into something 
bordering closely on the hypnotic state. Instead of going 



n Experimental Study of Sleep 45 

into the hypnotic state, however, as the fully developed 
human subject would occasionally do, the puppies went 
into sleep. 

What interested me most in the puppies was the fact of 
their habituation to the sleep-procedures. They seemed 
to like the whole procedure and had no objection to my 
manipulations, so that after a time I even ventured to put 
them to sleep on the table without wrapping the cloth 
round their limbs; the little fellows went to sleep as cheer- 
fully and as soundly as before. They lost all fear and 
lent themselves readily to the operations. It was thus 
sufficient for me just to put them down on their sides, and 
it did not matter on which (they would not sleep on their 
backs), when the puppies, of their own account, almost, 
went into their customary subwaking and sleep-states. 

Those puppies were gone and another puppy, an un- 
trained one of the same litter, had taken their place. This 
little fellow was about a couple of months old and was 
a hard nut to crack. He was sturdy, fat and refractory. I 
had quite a tussle with him. It took me more than half 
an hour to appease him. He became quiet for a few min- 
utes and seemed to have gone off into a passive condition 
closely bordering on sleep, but he was soon up and in arms 
again. Maybe the loud knocking in the adjoining room 
disturbed the experiments. 

I wrapped him all round in the cloth and shutting his 
eyes firmly with my fingers and holding him down tightly 
with my hands, I finally succeeded in moderating his ardent 
temper. The loud barking gradually subsided, and finally 
degenerated into growling. This growling really added to 
the monotony of the sensations. The growling then dimin- 
ished and the little fellow began to breathe more quietly, 
the heart-beat due to excitement subsided, and the puppy 
fell asleep. He slept quietly for about ten minutes only 
and woke up again. His eyes looked sleepy and he yawned 
for some time. 

An attempt was made to put him to sleep under the 
same conditions of monotony and limitation, but it was 
difficult to quiet him. He barked and struggled and re- 
fused to let himself be controlled. It was decided to let 



46 An Experimental Study of Sleep 

him go for that day. This condition kept on for several 
days. The most that could be done with him was to wrap 
him in the cloth, hold him firmly with the hands, and have 
his mouth shut. 

I confess that at first I almost despaired of ever break- 
ing the youngster into the game. I kept at him, however, 
and after a long series of trials the little fellow did not meet 
me any longer with such feelings of opposition. Finally 
one day after a hard tussle and a few severe shakings 
I decided to leave him to himself. To my great surprise 
the puppy became quiet, his eyes became perceptibly nar- 
rower, and at last he fell asleep. The sleep was very sound. 
He did not open his eyes when I changed the position of 
his paws, nor did he even open his eyes when I tickled the 
paws or pricked them. The only response to those stimu- 
lations was the reflex movement of the paws, drawing them 
away from the direction of the stimulus. The eyes were 
firmly shut, and when I attempted to separate the eyelids, 
the latter resisted quite perceptibly my efforts. When I 
did open the eyelids, the eyeballs rolled up and the pupil 
was contracted. The puppy slept for about half an hour. 
I decided to awaken him and see what he would do and 
also to observe the stages which he would pass in getting 
out of the sleep-state. The cloth was unrolled. This 
awakened him. He opened his eyelids, stretched his fore- 
paws and was going to sleep again; the eyes closed. On 
testing his forepaws, there was some resistance, though very 
slight, but it could be noticed on attempting to bend the 
paw at the joint. The eyes opened and closed; finally 
they opened fully and the little fellow stretched out his 
paws and yawned with a good relish as after a delightful 
sleep. At last then my long efforts were crowned with 
success. The puppy did fall asleep and in waking was 
observed to pass through the characteristic stages of hypnoidal 
states. 

The advantageous moment was then seized to push 
the matter for all it was worth, to again induce sleep under 
the conditions of monotony and limitation now that the 
puppy proved so obliging and went off into sleep on its own 
account. The cloth was wrapped round the puppy's limbs 



An Experimental Study of Sleep 47 

holding him down firmly. I closed his eyes with my 
fingers; the puppy, having been just awakened from his 
deep sleep, felt more gracious and did not kick much, opposed 
but little and in a few minutes fell into a deep sleep. After 
sleeping for about a quarter of an hour he was awakened. 
On awakening for a brief period the presence of the inter- 
mediary, subwaking, hypnoidal state was observed. I 
immediately proceeded to put him to sleep again, giving 
him no respite and plunging him rapidly in succession 
from waking into sleep and then again from sleep into 
waking states. This process was kept up a few times until 
it was quite certain that the little fellow was under control. 
The puppy got thus habituated to manipulations as well as 
to the rapid transitions from waking to sleeping and back 
again. Every time he was brought out of sleep the puppy 
was very quiet and did not resist my efforts to put him to 
sleep again. At first I did not dare to observe closely and 
especially to experiment on the first stages of going into 
sleep, lest I might disturb the puppy and thus break the 
charm, as I was anxious that he should first of all be habitu- 
ated to the process and to the sleep-states under the condi- 
tions of monotony and limitation and should cease to show 
resistance. After a number of experiments the puppy be- 
came tractable and thenceforth the experiments could 
be carried on without any further protests and rows on his 
part. 

From now on the experiments proceeded in peace. 
When occasionally the little fellow became obstreperous, 
a few shakings brought him to his senses. 

After wrapping the puppy in the cloth, and holding 
him firmly with both hands, I closed his eyes with my fin- 
gers. After a few seconds the puppy fell asleep. The 
eyelids were firmly closed. When an attempt was made 
to open them, they resisted; when the eyelids were sepa- 
rated forcibly, the eyeballs were found rolled up. There 
was contraction of the pupils and when darkened with the 
palm of my hand, the reaction was very sluggish. When 
the conjunctiva was touched with my fingers, there was a 
slight reaction of closing the eyelids and slight shifting of 
head and body, but the puppy remained asleep. He slept 



48 An Experimental Study of Sleep 

for about half an hour and was awakened for further experi- 
mentation. On awakening, the puppy passed as usual 
through the transient subwaking state characterized by 
slight catalepsy of the extremities. 

The puppy was put to sleep again with the cloth about 
his extremities; the forepaws were more or less loosened 
for observation and experimentation. The head was left 
protruded out of the cloth so as to observe the changes. 
This condition was always observed in my experiments on 
sleep, only in some cases the head was kept a little covered 
so as to keep out the light. In this case I had the head 
fully uncovered. My fingers were kept on the puppy's 
eyelids, but I removed them in a few seconds. The eye- 
lids were found partly closed and I observed a peculiar 
tremor of the eyelids similar to that found in human 
subjects before falling into the hypnotic state. The eyes of 
the puppy were shaded with the palm of the hand. Gradu- 
ally the eyelids closed tremulously. It could be distinctly 
seen how they opened partly, and then closed again. After 
the eyelids became fully shut, a peculiar phenomenon 
strikingly analogous to one manifested in hypnotic subjects, 
was observed; the puppy seemed to try to open the eyes 
but could not do it. He tried evidently quite hard to raise 
the eyelids, but only succeeded in raising a part of the lids, 
thus exposing a slit of the sclera; the eyeballs in this in- 
effectual effort of the puppy to open its eyes were seen to 
be rolled up. The eyelids closed again. The efforts on 
the part of the puppy to open its eyes were repeated a few 
times and each time the attempts were in vain. The eyelids 
then closed and remained so. This is so striking and so 
similar to what is observed in the hypnotic subjects that one 
is almost tempted to describe this condition as hypnosis. At 
any rate one is justified in saying that we observe here a 
phenomenon which is strikingly analogous to the hypnoidal 
state. In going, then, into the sleep-state the puppy passed 
through a state which is evidently on the borderland of 
sleep and what in the human subject is described as hyp- 
noidal. This borderland state forming an intermediary state 
between waking on the one hand, hypnosis or sleep on the 
other, is just what characterizes the subwaking, hypnoidal 



An Experimental Study of Sleep 49 

state. There seemed little doubt that in going into sleep 
the puppy did pass through hypnoidal states. 

Another fact that may be of interest in the sleep of 
this puppy, as well as of the other puppies under observa- 
tion, was the shivering in going to sleep. The extremities 
trembled when raised and a transient state of resistance and 
catalepsy was often observed. This catalepsy was specially 
pronounced when the forepaw or any other of the extremi- 
ties was extended and a little manipulated. It seems as 
if we give here a suggestion to the puppy, as is the case with 
the state of abnormal suggestibility in the human subject. 
I may add that these manifestations of the hypnoidal state 
were not so marked on awakening. 

After control was gained over the puppy he could be 
handled safely. It was thought it might be well for the 
sake of the experiment to irritate the dog a little and see 
what would be the result. He was forcibly pressed and 
choked very slowly so as to avoid the sudden onset of ex- 
citement. He yelped, but it seemed that the habit of going 
to sleep was even stronger than the excitement. In spite 
of all the irritation the puppy soon became quiet and when 
his hind limbs were wrapped around, he soon was disposed 
to fall asleep. With my fingers I just covered his eyelids, 
but did not press on them. It was just the merest sugges- 
tion of pressure on the eyes, but the little fellow went into 
a sound sleep. Before falling asleep I observed the usual 
blinking of the eyes, the opening and closing of the eyelids 
and twitching of the orbicularis palpebrarum as well as 
the rise and fall of the eyelids until the eye became com- 
pletely closed. On attempting to open the eyelids there was 
great difficulty in separating them. On examination the 
eyeball was found to be rolled up, the pupil contracted 
and not reacting to light. The conjunctiva was found 
almost insensitive. The dog responded to stimulations by 
reflexes of the forelimbs and on stronger stimulations by 
movements also of the hind limbs, but he did not wake up. 
At first the limbs were slightly resistive, especially when I 
manipulated them, pressing and kneading the muscles of 
the upper front leg. The cataleptic state of the extremi- 
ties was, as usual, only transient and the limbs remained 



50 An Experimental Study of Sleep 

during the whole state of sleep in a condition of relaxation. 
The same state, though slighter, was as usually, also present 
when the dog was aroused from his sleep by a summation 
of stimuli. 

The sleep-experiments were carried out on this formerly 
refractory puppy with great ease. In fact, the facility with 
which sleep was induced far exceeded the experiments 
performed on any of the animals handled before. It could 
only be compared to the ease with which a subject on 
repetition of hypnotization goes into hypnosis. Still it is 
not possible to regard the sleep of the puppy as hypnosis. 
There is no suggestibility present, nor that characteristic 
psychophysiological plasticity of associations and dissoci- 
ations during or after hypnosis. The state in which the 
puppy falls is nothing else than normal sleep. Only 
in passing into that condition there are present manifesta- 
tions which recall the hypnotic state. The reason is very 
simple, the puppy is passing through a state which is inter- 
mediary in character between waking state and sleep. 
This intermediary state is hypnoidal in nature and has 
some manifestations which are analogous to hypnosis in 
the higher and more developed mental states of man. In 
the dog we have the foreshadowing of what is afterwards 
fully found in man alone.- The hypnoidal state precedes 
and succeeds sleep. 

As I continued my sleep-experiments on the puppy, 
it became easier and easier to put the little one to sleep; 
so much so that after a time I could put the puppy into 
sleep, first passing through all the stages observed, though 
the cloth, that magic for the induction of sleep, was no 
longer used. I put the puppy on the table, just kept him 
quiet by patting him a little, and pretty soon off the little 
fellow went into the land of Nod. 

The puppy was put on the table, then laid down on 
his side — he did not resist, he kept as quiet as a little lamb. 
His eyes were shaded with a screen and the little fellow 
marched off into sleep. To produce sleep in the puppy 
after a few weeks' training was just child's play. The con- 
trast to his previous unmanageable condition was great 
indeed. It was now possible with the greatest ease to have 



An Experimental Study of Sleep 51 

him pass from sleep to waking and from waking to sleep. 
The contrast here was also very surprising, the puppy 
played, ran around, barked violently and in a few moments 
he was fast asleep with limbs relaxed and immovable, with 
eyes firmly closed, eyeballs rolled up, pupils contracted, 
conjunctiva anaesthetic, and all the sense-organs dulled and 
stupefied, as if by a hypnotic or anaesthetic. In a few 
moments more the puppy was up again, gave a yawn or 
two and was as restless and playful as ever. The transition 
from one state into the other was so rapid that it was almost 
marvellous. 

The puppy was found very restless, barking and jump- 
ing, but as soon as he was put on the table, his limbs were 
kept quiet for a few moments, his eyes shaded; his eye- 
lids began to blink and the muscles around the eyes to 
twitch, and the fellow began to shiver, not from fear, as 
the heart-beat was not accelerated, but slower, and the 
respiration was tranquil and lowered. The shivering was 
one of the phenomena observed in puppies, when on their 
way into sleep. What was specially interesting in the series 
of sleep-experiments was not only the significant fact that 
the puppy under the conditions of monotony and limita- 
tions was going off into sleep without resistance and delay, 
but that before going to sleep, when the eyes were about 
to begin to blink, and the eye-muscles to twitch, the little 
fellow raised his eyes to me and looked at me and then, as 
if satisfied that everything was all right, off he went into his 
sleep contentedly. This state is often observed in the hyp- 
notic subject. 

It seemed to me worth while to test whether the per- 
sonality of the experimenter had any influence. When 
putting the puppy to sleep, I called Dr. Cannon to see it 
to test the phenomena of the subwaking hypnoidal state. 
To my great surprise I found that I could not succeed with 
the puppy as well. There was some difficulty in putting 
him to sleep, although there was not really active resistance. 
It took me some time before I could put the puppy to 
sleep and then test for the hypnoidal state and show it to 
Dr. Cannon. There seems then to be a true personality- 
element present in the experiments. 



52 An Experimental Study of Sleep 

I then left the puppy for about a week. I wanted to 
see whether it would make any difference in the ease of 
putting him into the sleeping condition. After more than 
a week, I found that he did not submit so cheerfully as 
before. It took me fully ten minutes to put him in a state 
of sleep. Finally he did go into a sleeping condition with 
all the symptoms characteristic of the subwaking and sleep- 
ing state. In about a quarter of an hour he woke up, but 
soon fell asleep again and slept for another half hour, after 
which he was awakened. He seemed sleepy and looked 
ready to go to sleep again, which he really did after I had 
kept his limbs and body quiet for a few seconds and the 
eyes shaded. Thus the habit was quickly re-established. 

To bring the personality-coefficient, so to say, more to 
the foreground, I decided that the dog should be put to 
sleep under the same conditions of monotony and limitation, 
not by me, but by another person. I asked Mrs. S. to 
lend me a hand in the present experiments and see what 
she could do with the puppy in putting it to sleep. The 
puppy was kept quiet on the table without being put into 
the cloth as I had been lately conducting my experiments; 
but the result was not successful. Mrs S. then resorted 
to the old conditions, namely to the cloth. The puppy 
went to sleep, but after some considerable trouble, though 
I must say he did not show any fight as I should have 
expected. It was then easy enough to put him to sleep 
without any cloth, though Mrs. S. could not accomplish 
it as easily as I could. There is then present a personality- 
coefficient in putting the puppy to sleep, but the coefficient 
is very slight in the puppy at least. The conditions of 
hypnoidal states and sleep, namely monotony and limitation, 
are the most important. For Mrs. S. could put the puppy 
to sleep; it was only a matter of time. Monotony, limita- 
tion and inhibition may thus be regarded as the condi- 
tions under which we can induce in the dog sub-waking 
hypnoidal states and sleep. 

I may add that I also carried out similar experiments 
on a dog of six months old. As the dog was used to me 
I had no difficulty in inducing sleep. I made him keep 
quiet and then closed his eyes firmly. He went to sleep. 
When I tried to open his eyes, they resisted. When I 



An Experimental Study of Sleep 53 

opened them, I found the eyeballs rolled up, nictitating 
membrane over part of sclera, and pupils were contracted. 
There were present the same manifestations of hypnoidal 
states, the slight catalepsy on falling asleep and a similar, 
though somewhat slighter catalepsy on awakening. There 
was little difficulty in putting the dog to sleep. With the 
repetition of the experiments it was easier to put him into 
hypnoidal states and sleep under the conditions of monotony, 
limitations of voluntary movements and inhibition. The 
dog was very lively otherwise, but when put under the con- 
ditions of monotony and limitation of voluntary activity, 
he sank into a passive state and then into a state of sleep. 

We see, then, that dogs are subject to the same condi- 
tion of sleep-states as is the case with the other animals 
experimented upon. In fact the experiments on dogs bring 
out the fact that the conditions requisite to induce hypnoidal 
states in men also hold good in the case of dogs. The 
hypnoidal states, both on falling into, as well as rising from 
sleep, are far more pronounced in the dog than in the lower 
animals experimented upon; the states themselves come 
up far more closely to similar states observed in men under 
the same conditions of monotony, limitations and inhibi- 
tion than they do in lower animals, such as the frog, the 
guinea-pig or the cat. 

Phylogenetically regarded the hypnoidal is the primitive 
"rest-state" out of which sleep and hypnosis have become 
differentiated. The lower the animal the more insecure, 
the more instable are its "rest-states," The animal must 
be on the alert in its rest, and "sleep", if at all, with its eyes 
open, so to say. It must be quick to wake and run from 
danger or if it cannot get away, it must "freeze and feign 
death"; in other words it must be able for the sake of pro- 
tection to fall into a state of catalepsy. Hence the rest- 
states must partake of waking, sleep and hypnosis, that 
is, must be essentially hypnoidal in character. 

The experiments on dogs are more instructive than the 
ones carried out on the other animals, because they clearly 
bring out the general principle of monotony and limitation 
in the causation of sleep. Diminution in the variability of 
the volume of sensory impressions brings about the state of 
sleep. 



Chapter X 

Experiments on Children 

THE experiments on animals were followed by experi- 
ments on children. The subjects were of different 
ages ranging from infants a few days old, to child- 
ren twelve and thirteen years of age. 
It is well known that children usually fall asleep more 
easily than adults; they sleep longer and also more soundly. 
This is specially the case with young children and par- 
ticularly with infants. We know that an infant passes 
most of its time in sleep, when it does not eat. We should 
expect therefore that the material would readily lend itself 
to our present purpose of experimentation, — to the induction 
of sleep-states. Now as a matter of fact, I find that in a 
number of my cases dealing with children it is no difficult 
task to put them to sleep, or to induce some form of sub- 
waking state, hypnoidal or other closely allied to it. The 
child easily falls into a subwaking hypnoidal state which 
may either pass into hypnosis or into sleep. When trying 
to put children to sleep I have often obtained a hypnotic 
condition and on the other hand when attempting to put 
my little patients into a hypnotic state I have only suc- 
ceeded in putting them to sleep. Before going, however, 
into either the hypnotic or sleep-state, I observed by close 
examination the presence of the hypnoidal state induced 
under the conditions of monotony and limitation of volun- 
tary movements. 

Since limitation of the voluntary activity, limitation of 
the field of consciousness and inhibition all help to a greater 
monotony, we may characterize the whole set of conditions 
requisite for the induction of sleep as the conditions of 
monotony. In children and especially in infants voluntary 
activity and the field of consciousness are undeveloped and 
limited, we should expect that the child would form a far 
better soil than the adult for the induction of the interme- 
diary sub-waking states and sleep. This is precisely what 
we find to be the case. 

54 



An Experimental Study of Sleep 55 

Moreover, the mind of the child, and more particularly 
of the infant, specially depends on muscular activity and 
on the wealth of incoming sensory impressions. That is 
why the child and the infant take such delight in motor 
activity, — in tasting, testing, and handling things. If now 
the motor activity is limited and the main source of sensory 
impressions, such as sight, is restricted, and if the environ- 
ment is kept in a state of monotony, such as darkness and 
lack of auditory stimulations, or monotony is brought about 
by a continuous noise and buzzing of some instruments 
producing a uniform noise, the child, on account of the 
poverty of its inner mental life, easily falls into a subwaking 
hypnoidal state and then into sleep. 

This ease of induction of sleep is furthered by the com- 
paratively small amount of variability of conscious activity 
present in the child — the variability of mental content being 
an important factor in keeping up the freshness, continuity 
and qualitative intensity of consciousness. Now as the 
child depends entirely for the variability of its consciousness 
on muscular activity and external impressions, we can well 
realize that when those sources become limited and monot- 
onous, the child falls under the influence of all the important 
conditions requisite for the induction of sleep. The child 
in short, has no inner wealth of mental life to fall upon; it 
has little, if any inner resources; that is why it falls an 
easy prey to sleep and hypnosis, when the external resources 
lose their variability, become uniform and monotonous. 

It may be well, however, to point out the fact that the 
conditions of sleep are somewhat different in the case of 
infants of a few days or of but a few weeks old. Young 
infants sleep most of the time. The waking periods are 
brief and alternate with long periods of sleep. Really the 
infant's state is one of sleep and he only wakes to eat. 
We may characterize the infant's waking states as feeding 
periods. The perceptual world may be regarded as practi- 
cally non-existent for the infant — ego and non-ego are 
absent. The external world is in a chaotic state with no 
interests, even instinctive ones, as yet present. The sen- 
sory organs are as yet undeveloped and the sensory elements 
are all incoordinated and unrelated. Even the raw ma- 



56 An Experimental Study of Sleep 

terial going to make up the future world of the individual 
is still in an extremely imperfect state. In short, the 
material presented by the undeveloped sense-organs is 
chaotic, undifferentiated and is at its minimum. There 
is really no external world for the infant and whatever sen- 
sory impressions are present lack meaning and interest. 

But if the sense-material coming from the sense-organs 
which is to build up the infinite wealth of the external 
world is still undeveloped and lacks all significance, it is 
quite different with the sensations coming from the internal 
organs, from the viscera. The visceral, organic sensations 
stand out in the foreground of what may be regarded as 
the infant's consciousness. Visceral, sensory material forms 
the main substance of the infant's universe. Ccencesthesis 
plays the predominant, if not the only role, in the life of the 
newborn. We can fully realize the importance and signi- 
ficance of ccenaesthetic sensations in the case of the infant, 
because the processes of growth and nutritive functions 
are all engrossing. The newborn is a vegetative being; 
it is all belly, stomach; it is a little glutton, it has to grow 
and that very rapidly; it lives for that purpose — it eats and 
sleeps. The waking periods are sparse, short and far be- 
tween, the infant wakes to eat, and when filled to the point 
of regurgitation, it sleeps. 

In this respect it may be well to observe the character- 
istic motor reactions of the newborn; the sucking move- 
ments are the only ones that are well coordinated, respond- 
ing regularly to external impressions. Thus in my experi- 
ments I have long ago described the interesting fact that 
in his early life the newborn responds to external stimula- 
tions with sucking movements. If the infant, for instance' 
is put to the breast and has his fill and the sucking move- 
ments stop, they will again be reinstated by any stimula- 
tions of his sense-organs. Make noise close to the infant's 
ears or throw some rays of light on his eyes, or tickle him, or 
cause him pain, or tug at the nipple, and the infant responds 
with sucking movements. In other words, all reactions 
of the newborn are coordinated and essentially adapted 
to nutritive purposes. Nutrition and its psychic correla- 
tive, ccencesthesis, form the essence of the infant's early life. 



An Experimental Study of Sleep 57 

It is therefore clear that the conditions of monotony of 
external sensations and of limitations of voluntary activity, 
an activity really absent, as well as limitation of the field 
of consciousness, can hardly be of any import in the young 
infant. The gnawing of hunger, intestinal discomfort and 
pain play the only important role. In the early life of the 
baby visceral activity and its concomitant ccenaesthesis 
possess the greatest amount and intensity of qualitative 
variability that keep up the limited consciousness of the 
waking state. When the child is hungry, it is fidgety, cries 
and is awake; when hunger is appeased, the waking state 
lapses and the baby falls asleep. The waking state is a 
brief passing phase in the feeding of the baby, a feeding 
phase which begins and terminates in sleep. 

If now we take all that into consideration, we should 
not expect to meet with clearly defined subwaking states 
and sleep under the conditions of monotony and limitation 
in the case of the newborn as we find it to be the case in 
the lower animals a couple of weeks old, or as we find it in 
the fully developed man. The young of the lower animals 
have a shorter training period and have a far larger amount 
of ready made and easily developed instincts or psycho- 
motor reactions than the baby. When the newborn is put 
under the conditions of monotony and limitation of the 
incoming external impressions and under restriction of vol- 
untary activity which does not as yet exist in him, the results 
are necesarily unsatisfactory. If the infant is full to the 
point of regurgitation, it goes to sleep, and if it is hungry 
the closing of the eyes and the attempts to hold it down by 
force are often quite ineffectual. The baby keeps on cry- 
ing to the great discomfiture of the experimenter. The 
easiest and possibly the best way to bring about monotony 
in the newborn is to soothe the youngster's bowels. It 
again the young baby has indigestion, stomach-ache and 
cramps, closure of the eyes and holding the little one quiet 
without permitting him to kick will hardly do. In such 
cases the best way is to bring about monotony and limita- 
tion of ccencesthesis. Giving the baby to suckle may appease 
temporarily the active peristalsis of the intestines and the 
little fellow may pass into the land of Nod; or we may press 



58 An Experimental Study of Sleep 

uniformly on the abdomen and keep on rocking the little 
body at a uniform rate. By thus effecting a monotony and 
limitation of the bowel-consciousness and intestinal activity 
we can bring about a state of sleep. Still, even in the very 
young infants I succeeded, when the little one happened to 
be specially well disposed, in putting it to sleep by keeping 
it very quiet and closing its eyes. In one case I succeeded 
in putting to sleep a refractory infant under the usual con- 
ditions of monotony and limitation by closure of eyes and 
holding down the baby's extremities from being too active. 
Usually, however, in very young babies I somewhat modi- 
fied my proceedings of monotony and limitation by address- 
ing myself to the baby's inner intestinal consciousness. In 
older babies and young children of over a year, I did not 
vary my usual proceedings in the induction of sleep under 
the conditions of monotony, limitation of voluntary activity 
and of the field of consciousness. 

We may now pass to the experiments. I shall follow 
here the same course as in my account of the experimental 
work performed on the lower animals, I shall not burden 
the reader with unnecessary details, but shall give a few 
cases of experiments, typical of the rest. 

Boy of twelve days; he was quiet; he looked into 
empty space, seemed not to be specially hungry nor ill dis- 
posed. I covered his eyes with my hand and restrained 
the movements of his limbs. He wriggled a little under the 
restraint, but soon became very quiet. When after a min- 
ute's time I removed my hand from his eyes, the eyelids 
remained shut. Breathing was quiet and uniform. I 
tried to pull apart the eyelids and found them resistive. 
When I forcibly separated his eyelids, I found the eyeballs 
rolled up, pupils contracted. He slept this way for a few 
minutes. When he awoke I made a second attempt to put 
him to sleep, but this time with no success. The little 
fellow wriggled and squirmed. The eyes rolled incoordi- 
nately and looked vacantly into space. Closure of his eyes 
was of no avail. I then modified the procedure, patted 
his back, soothed his belly, and shut out the light from his 
vacantly blinking eyes. Gradually the little man relaxed 
his eyelids, began to work them and fell asleep. This 



An Experimental Study of Sleep 59 

time he slept for about a quarter of an hour. I then awak- 
ened him by summation of slight stimulations. During 
the course of awakening, I observed a short state of resis- 
tance in the extremities. He was again put to sleep in the 
same way and when going into sleep the same state of re- 
sistance and catalepsy of the extremities was observed. The 
sleeping state was very deep, inasmuch as the little fellow 
was not disturbed by any sensory stimulations and only a 
good shaking brought him out of this deep state of sleep. 

A girl of ten days; very quiet. I restrained her motor 
exuberance and with the other hand I closed her eyes; she 
at first resisted and cried, but after a couple of minutes 
she fell asleep. Respiration, quiet and equable. Eyelids 
resisted attempts to pull them apart. Eyeballs were found 
rolled up; pupils were contracted. I made another attempt 
and found it somewhat more difficult, but the child became 
quiet, had eyes closed for a couple of minutes and opened 
them again. The third time the success was even less 
marked. I then once more resorted to my method of back 
patting, bowel-soothing, by rubbing and patting the abdomen 
and monotonous rocking movements. The little girl was evi- 
dently pacified and went to sleep. When falling asleep, there 
was a short stage of catalepsy, the raised hand remained for 
a short period, a few seconds, in the position given to it, then 
a state of relaxation set in. This relaxation of the limbs did 
not persist during sleep, but now and then I could succeed 
in giving a cataleptic attitude to the arm. Soon the arm 
dropped and then again it was possible to put it into a cata- 
leptic condition. The sleep was evidently not stable; the 
little girl apparently kept on oscillating between sleep and 
waking state. It seems to me, however, that it is more 
probable that the sleep-state in young infants is not differ- 
entiated as it is in the case of adults or of older children. 
The phenomena of sleep also present some characteristics 
of hypnosis and hypnoidal states, possibly, because the 
states of hypnosis proper are as yet embryonic — hypnotic 
or hypnoidal manifestations thus appearing in sleep. 

Boy of ten days. I had great difficulty in putting 
him to sleep by the ordinary methods of closure and re- 
striction of muscular activity. I had to resort to my modi- 



60 An Experimental Study of Sleep 

fied method — patting, tapping and rocking until he fell 
asleep. In passing into sleep there was a slight state of 
rigidity and catalepsy of the limbs which soon changed to 
one of relaxation, but in the middle of sleep, when tested 
again for catalepsy, he developed one but it passed off and 
could not be again noticed until several minutes later I 
tested during that interval; limbs were found to be in a state 
of relaxation. 

The interesting fact about the infant's sleep is that 
once asleep the infant is not so easily roused. This fact 
is sometimes very striking, especially, when the child has 
had its fill, and still more, when it has had its bath. To 
arouse the infant from its sleep is then pretty difficult and 
I have worked hard over the baby before I could disturb 
its peaceful repose. Some of the infants I have occasionally 
found so deeply immersed in sleep that even shaking could 
not arouse them. I had to give up all attempts to bring 
them out of the state of Nirvana and had to wait for a more 
favorable occasion. 

Girl seven days old. Ordinary ways of putting to 
sleep did not work here and I had to resort to the rocking, 
patting and tapping before my efforts were crowned with 
success. The girl fell asleep in a state of rigidity and cata- 
lepsy soon replaced by relaxation. The eyeballs were rolled 
up, but the child was restless. I put her again under the 
same conditions of monotony and this time she slept more 
peacefully — I had in fact, some difficulty in waking her. 
The state of awakening was characterized by a greater resis- 
tance of the limbs than the sleep-state. Still, even in her 
sleep I could now and then discover a cataleptic state. The 
sleep of the infant appears to have a mixed symptomatology 
of sleep and hypnosis. The characteristic manifestations of 
sleep, however, predominate. 

Boy two weeks old. I left him in the same position, 
but only shut his eyes forcibly with my fingers for not more 
than twenty seconds. He opened the right eye after thirty 
seconds, and the left eye remained closed for a minute 
and a half. This incoordination is observed in young 
infants. He did not fall asleep, however, before I tried 
the monotonous rocking, the baby being placed with his 



An Experimental Study of Sleep 6 1 

belly downwards resting on the palms of my hands thus 
causing a uniform pressure. In sleep I observed a catalep- 
tiform state. Hands remained in the attitude given to 
them. This lasted for but a few seconds. 

I can induce sleep in the boy by the following pro- 
cedure which is really another modification of the conditions 
of monotony and limitation of muscular activity. I either 
rock him for a time, while sitting quietly in the chair or 
take him in my hands and walk around with him, which 
also induces monotonous rocking movements. During all 
this time I sing to him some monotonous ditty. Sleep is 
more rapid in its onset, when the belly is pressed with my 
hands uniformly. The boy's eyes begin to close, first 
becoming as if fixed, hazy and vacant. He closes the eye- 
lids, opening and closing them alternately, the eye is fixed 
in the same direction. The eyelids then close, then half 
open. The slit of the eye becomes narrower and narrower 
and finally the eyelids close and open no more; the little 
fellow is sound asleep. If his position is left unchanged, 
he remains asleep for a very long time. If, however, he 
is put in the crib, he wakes in about five or ten minutes. 

When the boy is six weeks old, I can induce in him 
sleep, by simply closing his eyelids and singing to him some 
monotonous ditty. When the boy is not tired and has had 
a good sleep before, he falls into a peculiar state. He is 
apparently not asleep and still he is unable to open his eyes 
for a couple of minutes and even more. When he is fatigued, 
he immediately goes into a deep sleep. 

Boy three months old. Can easily be put to sleep by 
monotonous stimulations usually of the character described. 
When asleep, he is slightly cataleptic; the lethargic condi- 
tion, however, predominates. The limbs remain for some 
time in the position given to them, although the position 
is a very uncomfortable one. When he rapidly falls into 
deep sleep, he often retains the limbs, especially the arms 
in the same position, however awkward, in which they were 
put at the moment when he fell asleep. 

In following the course of the child's sleep-states, I 
find that between the sleeping and waking states there is 
frequently, in fact there is almost always present, an inter- 



62 An Experimental Study of Sleep 

mediary period of semi-waking, semi-sleeping state, or what 
is found by me to be present in lower animals as well as in 
man, when falling asleep, namely a subwaking, intermediary, 
hypnoidal state. This state is of long duration, sometimes 
lasting several minutes. It begins with the contraction of 
the levator palpebrarum, with twitching and trembling of 
the eyelids, the eyes gazing vacantly into space. The eye- 
lids open and close unequally, the eyeballs begin to turn 
up, the pupil is contracted. If in this state, he is addressed 
in a caressing way with which he is familiar and which in 
the full waking state he greets with a smile and a kick, he 
now starts violently, the limbs going up, and he utters his 
peculiar cry of great fright. Often, however, when he is 
in this intermediary hypnoidal condition instead of passing 
back to the waking state, he falls into a deep sleep. When 
passing from this hypnoidal state into sleep, he is often 
seen to smile and almost laugh, occasionally he makes 
movements of mastication, sometimes gives a start and a 
cry, and keeps on sleeping. It is a form of hypnagogic 
or even dream-hallucinations. 

As to the states which form the transition stages be- 
tween sleep and full awakening or the intermediary states 
in his getting out of sleep, I have often had the opportunity 
to observe the following spontaneous manifestations. When 
the soundly sleeping child is awakened by a noise, he throws 
up his arms, as if in fright, half opens his eyes and falls 
immediately asleep again. The fingers of the hands remain 
open and extended, as if in a cataleptic state. When I try 
to close them, I find them resisting and after a time they 
close gradually. The rest of the body is in a state of 
relaxation. I observed it accidentally as the result of an 
unintended noise, but I since tried to reproduce some similar 
sudden noises and obtained like results. 

When the boy was three and a half months old, I put 
him to sleep under the usual conditions of monotony and 
limitations of muscular activity. He fell asleep, his right 
hand and fingers remaining in cataleptic state, he kept them 
in the same position when he went to sleep. The fingers 
were outstretched and the arm raised. I tried to bend one 
of the fingers, there was no resistance, but curiously enough 



An Experimental Study of Sleep 63 

as we find it to be in hypnosis, the finger soon returned to 
its former position. The arm remained in the raised posi- 
tion for about three and a half minutes and then gradually 
dropped. The child remained quiet in this position of 
fully relaxed limbs for about four minutes then suddenly 
gave a subdued cry of distress, probably due to some dream; 
the arms went suddenly up, especially the left one which 
remained in a raised position with fingers tightly closed. 
This lasted for about two minutes and a half. I tried to 
open one of the fingers, and met with no resistance. I kept 
the finger in state of extension for about a minute: as soon 
as I let the finger go, it returned to its original bent position. 
I soon observed him roll his eyeballs under the still tightly 
shut eyelids; then he opened his eyes, smiled at me and 
fell asleep again. As he was falling asleep with eyelids 
closed I could see the eyeballs roll, while the face retained 
its smile for a couple of minutes longer, as if smiling in his 
sleep at me. The state is evidently an almost fully devel- 
oped subwaking, hypnoidal phase, bordering on waking, 
hypnosis and sleep. In fact we observe here already the 
suggestibility of hypnosis which is on the way to become 
differentiated from sleep and hypnoidal state. 

We may now give a rapid review of experiments carried 
out on older children ranging from the age of four to the 
age of fourteen. The hypnoidal states become more marked, 
the hypnotic and even somnambulistic states come to the 
foreground, and we find that when sleep is induced we often 
get mixed manifestations of a subconscious order. Mixed, 
however, and still ill-defined as they are, when compared 
with the adult states, both the subconscious and sleep states 
are induced under similar conditions of monotony and limi- 
tation of voluntary movements. In trying to induce sleep 
we may get a subconscious hypnotic state and on the other 
hand in making an attempt to bring about a hypnotic state, 
we may get a state of sleep. A good deal depends on the 
fact whether or not we have eliminated the other conditions 
requisite for hypnosis, but not for sleep. The indispensable 
conditions, however, both for hypnosis and sleep are mo- 
notony and limitation of voluntary activity. These condi- 
tions are all the more indispensable as we have demonstrated 



64 An Experimental Study of Sleep 

from our experiments that in order to reach either hypnosis 
or sleep the intermediary, subwaking, hypnoidal state must 
first be passed through. This intermediary state between 
waking on the one hand and sleep and hypnosis on the other, 
can only be induced under the conditions of monotony and 
limitation of voluntary activity. 

A boy of four was put in a dark room; the metronome 
was set going, beating slow measure. The child was 
told to lie down on a lounge, stretch out his hands and 
legs and keep perfectly quiet. His eyes were then shut. 
After a few minutes his respiration became lowered and 
regular. He ceased to reply when talked to. At first 
his arm showed some slight rigidity, but soon after, the 
arm fell into a state of relaxation. He was not in a hyp- 
notic state as he did not answer any questions and did not 
take any suggestions. When after a quarter of an hour 
he was awakened, he did not remember anything about 
talking to him, nor could we obtain it of him by any methods 
reaching the subconscious. He was really asleep and did 
not perceive anything during that period. These experi- 
ments were repeated a number of times with the same 
results. I observed that unlike hypnosis which can be 
induced in rapid succession, one state not differing very 
much from the other, in this particular case as the induction 
of the state was repeated, it was more difficult to bring it 
about, the state became lighter and lighter and the child 
was brought out of it by talking to him. 

Boy of seven. I put him in a darkened room. My 
electric battery was set going. I told him to keep quiet and 
shut his eyes. After a few minutes he began to yawn, I 
told him to stop. He stopped and I soon observed that his 
little hand clutched mine convulsively, I tried the arm, 
raised it; it remained in the same position. I then chal- 
lenged him to open his eyes. He could not do it. I let 
him alone in a very passive condition; respiration regular 
and quiet. When after ten minutes I came to him again, 
I called him by name; he did not answer. When I began 
to talk to him, he woke up. During the ten minutes he 
passed into sleep. This transition from hypnosis into sleep 
was effected through the intermediacy of the hypnoidal 



An Experimental Study of Sleep 6^ 

state which forms the borderland of the waking and sleeping 
states. The general conditions of monotony and limitation 
of voluntary activity that favor hypnosis also favor sleep. 

Boy nine years of age. I put him into a chair, told 
him to be quiet and then closed his eyes. He was passive, 
answered my questions; could open his eyes when chal- 
lenged. When, however, left alone with his eyes shut and 
his limbs relaxed, he was found to be fast asleep. He did 
not answer any questions, did not take any suggestions, 
did not react to stimulations of medium intensity. When 
spoken to sharply, he woke up. Both before and after the 
sleep-state there was a short period when the passivity 
was quite marked and some resistance as well as disposition 
to leave the limb where it was placed, although he changed 
the position of the limb when challenged. In passing then 
into sleep as well as out of it he passed through the inter- 
mediate hypnoidal state. 

Girl of thirteen. When put under the conditions of 
monotony and limitation of voluntary activity, she fell 
from the transient hypnoidal state into hypnosis and thence 
into deep somnambulism. After an hour, when left to the 
monotonous state of her somnambulistic consciousness, she 
passed into typical sleep, as she ceased to answer ques- 
tions and woke up when the questions and suggestions were 
given to her in the usual insistent way. From somnambu- 
lism she passed into sleep. On other occasions, when closely 
watched, it was observed that this transition was effected 
through the intermediary hypnoidal state. The girl passed 
from the waking state into hypnosis and somnambulism 
and then again back into the hypnoidal state and then fell 
into sleep. 

Boy aged thirteen. I put him into a quiet state. Met- 
ronome was beating slowly. Voluntary movements of the 
boy were restricted. The boy was then told to close his 
eyes. I put my fingers over them and kept them shut for 
a few minutes. When I raised my hand, I found that his 
eyes remained closed. His arm, when raised remained in 
the same position. When his arm was bent, he could not 
extend it, but when after a few minutes I began to talk to 
him, he woke up. He was evidently in the hypnoidal state 



66 An Experimental Study of Sleep 

on the way to hypnosis or to sleep. On another occasion 
he actually fell into hypnosis not being able to move his 
eyelids or his arms and even took various suggestions. After 
a few minutes he ceased to be in communication with me 
and when suggestions were given to him as they had been 
given to him before, he did not take them, but woke up 
when loudly spoken to. In other words he fell asleep, and 
the loud voice disturbed his sleep. 

Boy of fourteen; he had difficulty in going to sleep 
under the conditions of monotony and limitation, but when 
these conditions were long continued, he finally went into 
the hypnoidal state. As I feared to disturb him by too 
much questioning I left him without change to his monoton- 
ous environment. After about a quarter of an hour he 
was fast asleep, snoring in the chair. 

Thus we find that in infants and children, as in the 
lower animals, sleep, hypnosis, and hypnoidal states are 
intimately related, sleep presenting complex manifestations 
of subconscious states which become fully developed in the 
adult. 



Chapter XI 

Motor Reactions and the Nature of Sleep 

BEFORE we conclude the account of the experi- 
ments it may be of interest to make a brief state- 
ment of a statistical inquiry in regard to our mode 
of going to sleep. It is usually supposed that 
the course and mode of our activities are due to voluntary 
decisions, that they are irregular, changeable with mood 
and caprice as our whimsical will is. We are free agents 
and anything we decide to do we can do in any old way; 
we do it just as we please and it does not matter to us what 
the course and arrangement be, provided the will wills it 
so. As a matter of fact we are far more creatures of habit 
and instinct than of reason and will. This holds especially 
true of our fundamental reactions, such as the induction of 
sleep. If we ask the ordinary person on which side he goes 
to sleep or on which side he falls asleep most comfortably, 
the question puzzles him at first. At the first blush it seems 
to him he can go to sleep on either side; it does not matter. 
When the question is repeated to him and made clear and 
he begins to think about it, he soon finds out that he has 
a definite way of going to sleep. Should he try to go to 
sleep in a somewhat different manner, he would find it very 
difficult to fall asleep. We have definite ways of reactions 
which are due either to habit or to the structural arrange- 
ment and mode of function of our organism. 

Manaceine in studying motor reactions in sleep has 
found that right-handed people react in their sleep with 
the left hand, while left-handed react with their right hand. 
I have similarly experimented on human subjects and could 
not confirm Manaceine's results. In my experiments on 
infants I found that in early infancy the reactions in sleep 
differ but little from that of waking state. The reactions 
are undifferentiated, but I found that later on in the course 

6 7 



68 An Experimental Study of Sleep 

of the child's development, the motor reactions mostly con- 
form to Pfluger's laws of reflex action. 1 To quote from my 
notes : 

Boy two weeks old; sound asleep. I tickled his left 
nostril: bilateral reaction, both hands are thrown up at 
once. When the tickling is more intense or more persistent 
and prolonged, motor reactions in both legs are induced. 
The same holds true in the case of the tickling of the right 
nostril, the reactions are bilateral and become more diffused 
bilaterally, if the stimulus is more prolonged or more intense. 

The baby reacted in the same way in the waking state, 
so that there was no difference in the reactions of the two 
states. 

When the baby is fast asleep, I tickle the right temple, 
the response is a slight reaction with the left hand. This is 
really accidental. On other similar occasions the reaction 
is of the right hand and sometimes the reaction is of both 
hands and also of both legs, according to the intensity or 
to the cumulative effect of the stimulation. 

I invariably found that a slight stimulation given the 
first time produced a reaction, while a second and third 
stimulation of the same intensity often produces no result. 

(*) The following are Pfluger's laws of reflex action. 

(I) Law of unilateral reflexes. 

If peripheral stimulations cause contraction in only half of the 
body, the contraction always occurs on the same side as the stimulus, 
and in general those muscles contract whose nerves arise from that 
segment of the cord, to which the irritated sensory nerve belongs. 

(II) Law of reflex symmetry. 

If the effects of stimulating a sensory nerve upon one side extend 
to the other side, only such motor fibres are called into activity which 
correspond with those which are already excited on the stimulated side. 

(III) Law of unequal contraction on the two sides. 

If the contraction is unequal on the two sides, the stronger reflex 
is always on the side of stimulation. 

(IV) Law of reflex irradiation. 

(1) When stimulation of a cerebral nerve causes reflex contrac- 
tion, the motor nerve concerned is invariably either in the same level 
as the sensory nerve, or it is further downward toward the medulla 
oblongata. (2) When stimulation of a spinal nerve causes reflex con- 
traction beyond its own segment, irradiation always takes place toward 
the medulla oblongata. 

(V) The law of three locations of reflex contractions. 

Upon stimulation of a sensory nerve, reflexes can occur in only 
three parts of the body. These are: 

(a) at the level of the stimulated nerve. 

(b) in parts innervated from the medulla oblongata. 

(c) in the whole body. 



An Experimental Study of Sleep 69 

Boy six weeks old. Tickling of the left ear excites at 
first movements in the head, in the trunk and then in both 
hands; when the stimulation is continued, the whole body 
becomes involved in the reaction, then the left hand is 
raised. The same holds true in the case of the right ear, — 
the movements are first in the head, then spread to the 
trunk, then to the lower extremities, then only to the side 
specially stimulated. In other words the reaction is at first 
diffused and then only becomes more special, — the hand is 
raised corresponding to the side stimulated. This mode 
of reaction holds true both in waking and sleeping states. 

Boy twelve weeks old. I observed an interesting phe- 
nomenon which may be described as that of associated 
movements. The infant has both hands in his mouth. 
When one hand is taken away from the mouth the other 
goes off simultaneously, as if an invisible power has pulled 
it away at the same time. 

Boy thirteen weeks old. When he was asleep, I tickled 
his left temple, he reacted with the left hand. Tickled his 
right temple, reacted with the left hand again. When the 
stimulus became more intense and prolonged, he moved 
his head, left hand and also the right hand. 

I tickled the left foot when the boy was asleep, both 
hands reacted, the left hand having the start; I tickled the 
right foot, both hands reacted, the left hand having the start 
again. 

Tickled the left temple; moved right hand; tickled 
right temple moved right hand again. The reaction is 
indeterminate, — sometimes it is bilateral and sometimes 
crossed. There actions do not conform to Pfliiger's laws. 
On the whole bilateral reactions predominate. 

When the child was asleep, I passed a pencil over the 
whole length of the left side of his face, — he reacted with the 
left hand first and then started with both. I passed the 
pencil over the right side of the face, he threw up both hands, 
the right having the lead. 

Now and then one can begin to observe the manifesta- 
tion of Pfliiger's laws. When the child was asleep, I tickled 
his right foot; he drew away the foot. When the stimula- 
lation is slight, the right foot alone reacted; when the 



JO An Experimental Study of Sleep 

stimuli became summated he also reacted with the right hand. 
The same holds true, when the left foot is tickled, — on slight 
stimulations the left foot is drawn away; on continuous 
stimulation the left hand also reacts. 

Reactions of four months' old babies and older con- 
formed more and more to Pfliiger's laws. 

Experiments on older children give results of like 
character. Boy of seven years; when asleep, I tickled the 
right side of his face, the right hand reacted; I tickled the 
left side of face, the left hand reacted. When stimulations 
became summated or more intense the whole trunk reacted. 

In experimenting on adults in the waking state the 
results are somewhat uncertain. When touching with a 
moistened object the right side of the face, for instance, and 
telling the subject to wipe it immediately, sometimes the 
right and sometimes the left hand reacts. One can often 
observe that when the subject reacts to sudden irritations, 
Pfliiger's laws hold good; and sometimes one can observe 
reactions with the left hand alone, the right hand being used 
for more differentiated movements. 

Experiments on adults, when asleep, almost entirely 
conform to Pfliiger's laws of reflex reaction, especially is 
this the case, if the person has his hands free or sleeps on 
his back. In cases of hypnoidal states and hypnosis, the 
reactions are somewhat modified. If the subject happens 
to react with one hand, he keeps on reacting with it. Thus 
when the subject is touched with a wet or irritating object 
and is told to react, if it be the right side, he reacts with 
the right hand. If now the left side is similarly stimulated, 
the right hand keeps on reacting crossing to the left side. 
This takes place, even if there is a long series of stimula- 
tions, — the subject reacts with the hand he first starts to 
react with. This may be largely due to subconscious sug- 
gestion. I observed similar reactions in very suggestible 
subjects even in the waking state. 

Manaceine's results are not confirmed by me, and still 
there is some truth in Manaceine's statement. Now I 
have suspected for some time that if the condition of limi- 
tation of voluntary movements is one of the important 
factors in the induction of sleep, we should expect that it 



An Experimental Study of Sleep Ji 

would not be a matter of indifference on which side we rest. 
We should expect that, if the right side is the more active, 
that the limitation of the voluntary movements would be 
more marked on that side. In carrying on my experiments 
on children and adults when in their sleeping states, I had 
occasion to observe that there was a definite course in the 
motor reactions, in the process of falling asleep. There is 
method in sleep. Some people go to sleep only on their back 
and find it difficult to fall asleep otherwise, while others 
who go to sleep on their side and who form the greater 
majority always go to sleep on the same side; there are 
very few who can fall asleep indifferently on either side. 
Moreover, my observations have shown me that by far the 
majority of right-handed people go to sleep on the right side, 
while left-handed people go to sleep on their left side. I 
further verified this interesting fact by statistical inquiry 
among my patients as well as among Harvard students. 
Some of the right-handed people who go to sleep on the 
right side may after some time turn to their left to change 
position, while others keep on sleeping on the same side 
through the whole night. The majority change position, 
the right-handed to the left and the left-handed to the right. 
More than seventy-five per cent of right-handed people have 
given records to the effect that they sleep on the right side 
or rather fall asleep on that side. Of the left-handed per- 
sons, I find only one out of ten who falls asleep on the right 
side. One case is specially interesting to quote: "Up to 
my seventh year I slept on my right side and I was right- 
handed. At about the age of seven I met with an accident, 
I was run over by a team and my right side was injured so 
that I could not use the limbs of the right side. I used my 
left hand only, I began to sleep on my left side. This I 
did up to my fifteenth year. I then began to practice with 
my right hand too and am now ambidextrous. I sleep 
now on either side. I use both hands." 

Some claim that the reason why they sleep on the right 
side is because of the dreams produced by the pressure of 
the heart when sleeping on the left; but it is interesting to 
observe that others sleeping on their left write in their 
accounts that they cannot sleep on their right side, because 



72 An Experimental Study of Sleep 

of the bad dreams, restlessness and nightmares produced. 
Some claim that it is simply a matter of habit, but the very 
fact that habit should give such a large percentage of right- 
handed, sleeping on the right side,and of left-handed, sleeping 
on their left side, points to a fundamental condition of our 
functioning activities and mode of rest. This condition 
we have found in the variability of our consciousness, 
by the ceaseless variations of the incoming sensory 
impressions from sense organs, muscles, joints and various 
other organic activities. The kinesthetic sensations coming 
from the motor activities of our muscles and joints are very 
important in this respect. To bring about a state of rest 
and sleep, we must have the condition of monotony and 
limitation of voluntary movements, hence we can well see 
the reason why right-handed people whose right side is 
more active limit that side, while left-handed people prefer 
to limit the left side most active in them. We can also 
partly account for Manaceine's results, namely that in 
sleep, right-handed people react with their left hand which 
remains free as they sleep on the right side, while left-handed 
people react in sleep with their right hand, because they 
sleep on their left side. Manaceian's explanation is 
pointless in referring these reactions to the activities of the 
right and left hemispheres. According to Manaceine the left 
hemisphere of right-handed people is fatigued and hence in 
sleep the right hemisphere and the left hand have the ascen- 
dency. This explanation is fanciful and does not agree with 
facts. For when the experiments are carried out rigorously, 
the reactions are found to conform, with the exception of very 
youn infants, to Pflugers laws. 

Thus the experiments and observations made on lower 
animals, infants, children and adults all point in one direc- 
tion, they point to the fundamental conditions of sleep, to 
monotony and limitation of voluntary movements. Taking 
as my motto the dictum "hypotheses non fin go" I strictly 
followed the logic of facts. Sleep is not so much due to 
merely cutting off sensory impressions, be they intense or 
faint, as to the monotony of sensory impressions which in 
fact may even be intense and numerous. It is the invari- 
ability of sensory impressions that reduces the organism 
to the passive state which we experience as sleep. 



PART II 
THEORETICAL 



Chapter XII 
Cell-energy, Threshold, "Stimulus-exhaustion" and Sleep 

WE may advance in a tentative way the following 
theory which should be regarded as a pro- 
visional hypothesis of the causation of sleep. 
One of the main characteristics of living 
protoplasm is its adaptability to the conditions of the ex- 
ternal environment. External stimuli give rise to reactions 
of adjustment on the part of living substance. This prop- 
erty known in physiology as irritability is specially charac- 
teristic of all living matter or of what Huxley so aptly de- 
scribes as "the physical basis of life." Verworn defines 
the irritability of living substance "as its capacity of reacting 
to changes in its environment by changes in the equilib- 
rium of its matter and its energy." In other words, living 
tissue responds to external stimulations with some discharge 
of energy. The form of the discharge depends on the 
peculiar protoplasmic structure, according as it is muscle, 
gland, nerve cell or but slightly differentiated protoplasm, 
such as amoeba or bacterium. The character of the reac- 
tion to stimuli depends on the state of organization of the 
living tissue. 

The delicacy of response of living matter to external 
stimuli has its limit. Very weak stimulations do not call 
forth any reaction. Living tissue can only be set into activ- 
ity by stimuli of certain intensity. If the stimulus falls 
below that intensity, the protoplasm does not react. This 
holds true of all cells, from the simplest bacterium and infu- 
sorium to the most highly differentiated muscle-cell or neu- 
ron. The minimal intensity below which the stimulus 
remains ineffective is regarded as the threshold of stim- 
ulation. As Howell puts it: "A stimulus too weak 
to give a response with a motor nerve is usually designated 
in physiology as subliminal; a similar stimulus with sen- 
sory nerves is frequently expressed by the equivalent term 
of subliminal, that is below the threshold, so a stimulus 
just strong enough to provoke a perceptible reaction is the 

75 



76 An Experimental Study of Sleep 

minimal stimulus for efferent nerves and the threshold 
stimulus for sensory nerves." "Exceedingly feeble stimuli" 
says Landois "are without effect. The degree of intensity 
of stimulation that originates the first trace of sensation is 
called the threshold of sensation or the threshold-value." 
The same is more clearly put by Verworn: 

"Let us imagine an organism or part of an organism, 
e.g., a muscle, under conditions in which no stimulus affects 
it, and let us bring to bear upon it a stimulus, e.g., the gal- 
vanic current, which varies in intensity from zero upward 
and can be graded easily and delicately. Then we should 
expect the muscle to exhibit phenomena of stimulation, i.e., 
to perform a contraction, as soon as the intensity is increased 
above 0. But this does not happen. The intensity can 
be increased considerably before the muscle performs even 
the slightest twitch. Only when the intensity has reached 
a certain degree does the muscle respond with a contrac- 
tion; from here on the contraction is never wanting, and 
up to a certain degree becomes more energetic the more 
the intensity is increased. The stimulus, therefore, begins 
to operate only at a certain intensity, and this point is termed 
the threshold of stimulation. Below the threshold the stimu- 
lus is ineffective; above it the effect increases with the 
increasing intensity of stimulus. For the different forms 
of living substance the value of the threshold is very differ- 
ent. Thus, nerve-fibres are put into activity by extremely 
feeble galvanic stimuli, while Amoeba demands very strong 
currents. The same is true of all other varieties of stimuli 
in relation to the various forms of living substance." 

Psychologically we may agree with Stout that "the 
point at which it (the stimulus) is just indistinguishable, — 
so that the least increase would make it distinguishable is 
called stimulus-threshold." | 

Kiilpe's definition is short; "the just noticeable stimu- 
lus is technically termed the stimulus-threshold (die Reiz- 
schwelle)." 

With the increase of stimulations the irritability of the 
living substance diminishes, the threshold rises. The same 
minimal stimulus will no longer bring about a reaction, the 
stimulus must be increased in intensity before any effect 



An Experimental Study of Sleep 77 

can take place. Perhaps the best account of it is given by 
Verworn in his "General Physiology." 

"If a living object be stimulated by long-continued, 
oft-repeated, or very strong stimuli, after some time it passes 
into the condition of fatigue. The general characteristic 
of fatigue is a gradual decrease of the irritability of the 
living substance. This is expressed especially in the fact 
that with increasing fatigue, the intensity of the stimulus 
remaining the same, the result of the stimulation becomes 
constantly less. 

"We have already become acquainted with some ex- 
amples of this fact in considering galvanic stimulation. If 
a constant current of average strength be passed through 
an Actinosphcerium, at the moment of making, there begin 
to appear at the anode marked phenomena of contraction. 
The protoplasm of the pseudopodia flows centripetally 
until the latter are drawn in. Then the walls of the vacu- 
oles break; and a granular disintegration of the protoplasm 
results, which proceeds constantly farther from the kathode 
during the passage of the current. This disintegration, 
beginning with great energy, becomes slower and less ex- 
tensive the longer the current flows, and after some time 
is at a complete standstill. This means that the living sub- 
stance of the Actinosphcerium becomes fatigued in the 
course of continual stimulation, and decreases in irritabil- 
ity; hence the stimulus, which at first induced pronounced 
phenomena of disintegration, later produces no reaction 
at all. Pelomyxa is fatigued still more rapidly than Acti- 
nosphcerium. Stimulation for a few seconds is sufficient 
to make individuals of this genus wholly non-irritable to 
currents of equal intensity; a much greater intensity is 
then required to call out the same reaction/' 

The principle of variability of stimulation is of great 
importance in the reaction of nerve-tissue. When the stimu- 
lus remains invariable, both in intensity and quality, no 
reaction follows. This is clearly brought out in experi- 
ments on nerve-tissue. "The electrical current" says 
Landois,' "exerts its strongest irritant effects upon a nerve 
at the time of its entrance into the nerve and at the time 

1 Text-book of Physiology. 



78 An Experimental Study of Sleep 

of its disappearance. In like manner any rapid increase 
or decrease of the current passing through a nerve has a 
strong irritant effect. If on the other hand, the current 
be allowed to pass gradually into the nerve trunk or to dis- 
appear, or the current passing through the nerve be gradu- 
ally increased or diminished, the visible signs of nerve irri- 
tation are much less marked. In general, the stimulation 
is most pronounced the more rapid the current-variation 
within the nerve, that is the more suddenly the strength of 
the current passing through the nerve is increased or dimin- 
ished." This holds true in the case of the nerve, in which 
as Bowditch has shown there is little or no fatigue; where 
fatigue is present the principle of variability becomes a 
factor of the utmost consequence. The principle of vari- 
ability of stimulation plays a very important role in cells 
in general, and in nerve-cells in particular where fatigue 
easily sets in and the threshold is raised with the continu- 
ation of stimulation and with the successive discharges of 
cell energy. Variability of stimulation and fatigue influence 
the fluctuations of thresholds. 

It may be well to bring here the recent work of Sher- 
rington in regard to the relation of neuron threshold and 
the discharge of neuron energy. Sherrington points out 
that among the characteristic differences between conduc- 
tion in nerve-trunks and in reflex arcs (where nerve-cells 
are interpolated), we find in the latter "Irreversibility of 
direction instead of reversibility as in nerve-trunks, fatiga- 
bility in contrast with the comparative unfatigability of 
nerve-trunks," and "much greater variability of the thresh- 
old of stimulus than in nerve-trunks." Sherrington points 
out that "in certain cases, especially in Invertebrata, obser- 
vation (Apathy, Bethe, etc.), indicates that many nerve 
cells are actually continuous one with another. It is note- 
worthy that in several of these cases the irreversibility of 
direction of conduction which is characteristic of spinal 
reflex arcs is not demonstrable; thus the nerve net in some 
cases e.g. Medusa, exhibits reversible conduction (Romanes, 
Nagel, Bethe and others). But in the neuron-chains of 
the gray centred system of vertebrates histology on the 
whole furnishes evidence that a surface of separation does 



An Experimental Study of Sleep 79 

exist between neuron and neuron. And the evidence of 
Wallerian secondary degeneration is clear in showing that 
that process observes strictly a boundary between neuron 
and neuron and does not transgress it. It seems therefore 
likely that the nexus between neuron and neuron in the 
reflex arc, at least in the spinal arc of the vertebrae involves 
a surface of separation between neuron and neuron " "In 
view therefore of the probable importance physiologically 
of this mode of nexus between neuron and neuron it is con- 
venient to have a term for it. The term introduced has 
been synapse." "At each synapse there is a neuron thresh- 
old. At each synapse a small quantity of energy, freed in 
transmission, acts as a releasing force to a fresh store of 
energy not along a homogeneous train of conducting material 
as in a nerve-fibre pure and simple, but across a barrier 
which whether lower or higher is always to some extent 
a barrier." 1 

Assuming then the principle of variability of stimula- 
tion of neuron energy and neuron threshold in regard to the 
liberation of neuron energy, principles advanced in my 
previous works, we can return to our subject under dis- 
cussion, namely sleep. We may regard sleep as a reaction 
of protoplasm and as such we may express it in terms of 
neuron threshold and neuron energy liberation. 

If a series of stimulations are kept up without variation, 
the sensory threshold gradually rises and finally the stimuli 
fall out of consciousness, they fail to awaken the psycho- 
physiological systems which have responded to the same 
stimulations before, because of the rise of the thresholds. 
This psycho-physiological law, characteristic of all tissues 
and psycho-neural systems, underlies the phenomena of 
sleep. As the cell or the neuron keeps on reacting to 
stimulations the disposable physiological energy becomes 
lowered and there is greater economy in the liberation of 
cellular or of neuron-energy. The cell or neuron does not 
respond to the same intensity of stimulus with the same 
amount of energy. In other words, the threshold rises. 
Should the stimulation keep on acting without variation, 
both as to quantity and quality, the threshold rises so high 
that the stimulus can no longer step over the threshold and 

1 Sherrington, "The Integrative Action of the Nervous System." 



80 An Experimental Study of Sleep 

can no longer call forth any reaction in the cell. We say 
that the cell or the neuron is fatigued or exhausted. Really 
this is not so much due to the exhaustion of the cell as to the 
exhaustion of the stimulus, — it is the stimulus that has 
exhausted itself. Vary the stimulus in quantity or in qual- 
ity and the cell or neuron reacts once more. 1 We may 
possibly best describe this general physiological fact of 
cellular reaction by the term of " stimulus-exhaustion." 
By repetition the stimulus exhausts itself and can no longer 
call forth a reaction in the cell, although the cell may other- 
wise possess a large amount of disposable energy. 2 

As far as the particular stimulus is concerned the cell may 
be regarded as asleep. The stimuli are withdrawn. Put- 
ting the same general law in different terms we may say 
that sleep is produced by monotony. 

The cell or the neuron may be regarded as a reservoir 
of energy. With the great biologist, Strassburger, we 
may describe the cell as " energid." Conceived in terms 
of energy the cell possesses various levels of energy. The 

1 This may be related to the interesting experiments referred to by 
Sherrington: 

"When the scratch-reflex elicited from a spot of skin is fatigued, the 
fatigue holds for that spot, but does not for the reflex as obtained from 
the surrounding skin. The reflex is then tired out to stimuli at that spot 
easily obtainable by stimulation two or more centimetres (half an inch) 
away. This is seen with either mechanical or electrical stimuli." 

{The Integrative Action of the Nervous System, Sherrington) 

2 "The singleness of action from moment to moment thus assured 
is a keystone in the construction of the individual whose unity it is the 
specific office of the nervous system to perfect. Releasing forces acting 
on the brain from moment to moment shut out from activity whole 
regions of the nervous system, as they conversely call vast other regions 
into play." 

"An arc under long continuous stimulation of its receptor tends 
even when it holds the common path, to retain its hold less well. Other 
arcs can then more readily dispossess it. A stimulus to a fresh arc has, 
in virtue of its mere freshness, a better chance of capturing the common 
path." 

"This waning of a reflex under long-maintained excitation is one of 
the many phenomena that pass in physiology under the name 'fatigue.' 
Its place of incidence lies at the synapse. It seems a process elaborated 
and preserved in the selective evolution of the neural machinery. It 
prevents long continuous possession of a common path by any one reflex 
of considerable intensity. It favours the receptors taking turn about. 
It helps to ensure serial variety of reaction. The organism, to be suc- 
cessful in a million-sided environment, must in its reactions be many- 
sided." 

(Sherrington, Address British Association for the Advancement of 
Science, 1904). 



An Experimental Study of Sleep 8 1 

main levels of cellular energy have been described by me 
in former works as dynamic, static and organic. 

By dynamic energy is meant that portion of energy 
which the cell can dispose of in its relations and reactions 
to the stimuli of the external environment. 

By static energy is designated that portion of energy 
which is used only for the life maintenance of the cell, both 
in relation to other cells and to its own molecular consti- 
tution. It is the energy requisite to keep up its morpho- 
logical organization and internal physiological functions. 

By organic energy is meant the energy contained in the 
tissues of the dead cell not as yet decomposed into its inor- 
ganic constituents. 

The levels of cellular energy are not different in kind. 
They merely represent progressive phases or stages of the 
same process of cellular activity. 

In its relations with the external environment, the cell 
does not utilize the whole of its dynamic energy. A large 
amount of it lies fallow, so to say, and remains inaccessible 
to the ordinary stimulations of the external environment. 
This amount of unused energy may be termed stored, reserve 
energy. 1 For the cell stores up energy as it stores food, in 
order to be able to meet the various emergencies that may 
arise in the course of its relations with the external world. 
In respect to storing up energy the law of stimulus- 
exhaustion may be regarded as a safeguard to the cell. The 
same qualitative stimulus cannot draw more than its allotted 
portion of energy. If the stimulation continues and attempts 
to draw more than its share the door, so to say, closes and 
the stimulus knocks in vain against a locked door. The 
threshold rises with each successive stimulation. When the 
maximum amount is drawn, there is no longer response to 
that particular stimulus, or rather to say, to that particular 
qualitative stimulation of a definite intensity. In regard to 
it the cell no longer reacts, — it is asleep. In order to 
respond again to the particular stimulus of a certain intens- 
ity and quality, the cell must recuperate its special form of 
energy. When this recuperation is effected, the cell is 
once more ready to react to the given stimulus. 

1 See my Studies in Psychopathology, Boston Medical and Surgical 
Journal, 1907. 



82 An Experimental Study of Sleep 

The liberation of cellular energy in response to external 
stimuli may be regarded as the active waking states, while 
the restitution or passive rest-states of the cell, during which 
the threshold is raised and cellular recuperation takes place, 
may be regarded as sleeping states. 

From the standpoint of cell metabolism, waking states 
are correlative with katabolic changes, while sleeping states 
are correlative with anabolic conditions. When the cell is 
active and awake, it liberates energy; when it sleeps, it 
stores energy. This process of storing up energy is going 
on all the time to some extent. If a stimulus of a certain 
intensity and quality keeps on liberating energy, it may 
arrive after some time at the maximum, when the threshold 
rises so high that the cell no longer reacts. 1 In respect to 
that stimulus the katabolic, active, waking state ceases and 
is replaced by the anabolic, sleeping states. The cell may 
thus be awake to all other stimulations, but in regard to 
the special stimulus it is asleep. We may say that the cell 
is asleep partially. When the liberation of energy has 
reached the maximum point, and the thresholds are raised 

1 "Whenever by a stimulus applied to an irritable substance, the 
potential energy there stored up is liberated the following phenomena 
may be observed: (1) A so-called latent period of variable duration 
during which no effects of stimulation are manifest; (2) A very brief 
period during which the effect of stimulation reaches a maximum; (3) A 
period of continued stimulation during which the effect diminishes in 
consequence of the using up of the substance containing the potential 
energy — i.e., a period of fatigue; (4) A period after the stimulation has 
ceased in which the effect slowly passes away. 




The curve dra-wn by a muscle in tetanic contraction, as shown iu 
the diagram, illustrates this phenomenon. Thus, if AD represents the 
duration of the stimulation, AB indicates the latent period, BC the period 
of contraction, CD the period of fatigue under stimulation, and DE the 
after-effect of stimulation showing itself as a slow relaxation. When 
light falls upon the retina corresponding phenomena are to be observed." 

An American Text-Book of Phvsiologv, William H. Howell, Vol. 
II, p. 343. 



An Experimental Study of Sleep 83 

in regard to most or to all the ordinary stimuli of the external 
environment, the cell may be said to be fully asleep. 

Should however, the liberation of energy by various 
stimuli keep on and begin to liberate the reserve energy 
levels and then pass over into the levels of static energy, the 
cell falls into a pathological waking state. 

We may represent the relation of the different levels 
and their correlative states by the following diagram. 

What is true of the cell holds also good of systems of 
cells and neurons constituting a multicellular organism. 
The condition of monotony and the law of stimulus-exhaus- 
tion play a very important role in the various changes and 
adaptations of life-activity. Stimuli which have exhausted 
themselves by their monotony drop out and are replaced by 
new ones until the whole round of stimuli is gone through 
and the organism ceases to respond to its external environ- 
ment, — falls asleep. 

The rise of threshold after stimulation holds true in 
the whole domain of biological activities. If the gastroc- 
nemius muscle of the frog, for instance, is stimulated, say 
by an electric current, the muscle with successive stimula- 
tions responds less readily with contraction and this becomes 
more evident with the onset of fatigue. Pffefer in a series 
of extremely interesting experiments has shown that sper- 
matozoids of ferns are attracted by malic acid, the pro- 
gressive response of the attraction of the cell requiring 
a constant increase of the degree of the concentration of 
the acid, the increment of stimulations bearing within cer- 
tain limits a constant ratio to the total stimulus. The 
threshold rises with each successive stimulation. 

In the sphere of sensation we find the same rise of 
threshold. We are all acquainted with the fact that an 
additional candle or lamp, for instance, in well lighted 
room does not produce the same sensory effect as when 
brought into a more or less dark room. An electric light 
in the sun is scarcely perceptible. An additional ounce 
to a lifted pound does not feel as heavy as when raised by 
itself. A sound added to another sound or to a noise sounds 
less loud than when appearing isolated or when the same 
sound is breaking upon silence. The same relation holds 
true in the case of other senses. 



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An Experimental Study of Sleep 



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An Experimental Study of Sleep 85 

This same truth is still more clearly brought out in the 
fact that if we take a certain stimulus as a unit giving rise 
to a definite sensation, then as we progressively ascend 
and add more and more, units of the same stimulus, the 
qualitative intensity of the sensation is far from rising pro- 
portionately. If we take for instance, the weight of an 
ounce as our unit of stimulation, then the successive moments 
of unit-stimulations, that is of ounces, will not give rise 
to as distinct and similar sensations as did the initial stimu- 
lation. The second ounce will give a sensation fainter 
than the first one and the third fainter than the second 
and so on until a point is reached, when the sensation of 
an additional ounce will not at all be appreciated, will 
dwindle away and almost reach the zero-point. In the 
same way, if the pressure of a gramme is excited in the 
hand, successive increments of grammes will not in equal 
degree increase the sensory effect. The additional incre- 
ments of grammes, though they are equal units of stimula- 
tion, give rise to fainter and fainter sensations, until finally 
all sensory appreciation of the added unit fades away and 
disappears. If the hand is immersed in water say at the 
freezing point, an addition of ten degrees will be perceptibly 
appreciated, while successive increments of ten degrees 
each will be felt less and less and finally will not be noticed 
and will become difficult to detect. In short, the threshold 
rises with each successive stimulation. 

To bring about a sensory response of an already stimu- 
lated sense-organ the intensity of the stimulus must be 
relatively increased. This is what constitutes Weber's 
law. The continuous progressive sensory response of a 
sense-organ requires a constant increase of stimulation 
which within certain limits, bears a constant ratio to the 
total stimulus. 1 This law is sometimes summed up by 

1 By noting for each strength of stimulus the addition required to 
evoke a just perceptible alteration of sensation, a series of quantities is 
obtained expressing the law according to which sensation alters when 
stimulation is increased. This expression is the so-called "law" of Weber. 
It says that a given stimulus is perceived less when added to a large than 
to a small one, or that an addition to a large stimulus is perceived less 
than an addition to a small one, unless it, relatively to the stimulus, is 
as great. The "law" may be phrased variously in physiological theory. 
It may be interpreted as not physiological at all, but psychological. The 



86 An Experimental Study of Sleep 

physiologists and psychologists in the statement that the 
stimulus rises in a geometrical and corresponding sensa- 
tion in an arithmetical progression, or as Fechner expresses 
it, " the sensation varies as the logarithm of the stimulus. " 
We are probably nearer the truth, if we limit ourselves to 
the statement that " the increase of the stimulus necessary 
to produce a just perceptible difference in the sensation 
bears a constant ratio to the total stimulus." In short, 
activity raises the threshold. The phenomena fall under the 
law of stimulus-exhaustion. Each reaction to an external 
stimulus raises the threshold of that stimulus and with its 
repetition becomes finally excluded, temporarily, at least, 
from the cycle of living stimuli, that is, such as are capable 
of bringing about reactions and adjustments to the external 
environment. The excluded stimulus is ignored, becomes 
non-existent for the organism. The organism is asleep for 
that stimulus. 

In the course of the daily activity of the individual the 
thresholds of sensitivity and of sensori-motor reactions in 
response to the stimuli of ordinary life rise gradually, the 
stimuli fall below the threshold of living reactions. The 
mass of stimuli of the external world constituting the exter- 
nal environment of the individual drops out of the life-cycle 
of the individual and for the time being ceases to exist for 
him. The individual is asleep, asleep for that environ- 
ment. In other words the stimuli of the external world 
by their continuous action have become monotonous, have 
raised the thresholds and have become excluded from the 
life existence of the individual who is now deeply asleep for 
that given environment. 

disproportion between increment of stimulus and increment of sensation 
may take place in purely psychological events and processes. Wundt 
is of that opinion. He points to the wide occurrence of such a ratio in 
all psychical activity as outcome of the relativity inherent in every con- 
scious process. Waller finds the response in a nerve trunk directly 
stimulated, as judged by action current, increase much more nearly 
directly as the increase of external stimulus than does the response from 
muscle when nerve is stimulated, or from nerve when retina is adequately 
stimulated. Waller's evidence seems to point to the law being in part 
a function of the nerve-cell endings; probably, therefore, applicable to 
synapses as to motor plates. Delbceuf considers the law an expression 
of ever-increasing proportion of loss of effect in the central nervous 
system, due to "fatigue." (Sherrington in Schafer's Text-Booh of Physi- 
ology, Vol. II, p. 981.) 



An Experimental Study of Sleep 87 

Should an appreciable variation occur in the environment 
at about the time when the organism is ready to fall asleep 
the external world becomes again a living reality. The 
individual becomes alive and wide awake to what is going 
on around him. If an appreciable change in the total mass 
or in some stimuli constituting the environment takes place, 
the individual may be awakened out of his sleep. Should 
the variation occur in some of the stimuli, their thresholds 
become lowered and the individual, though asleep in regard 
to all else, is awake in regard to them. This partial wak- 
ing state is the soil in which dreams develop most luxuri- 
antly. We do not dream, when we are asleep, we dream, 
when we are awake. 1 

The individual may be asleep to all else and still be 
awake to special stimuli whose thresholds are very low. 
The mother watching over her babe, the nurse, the physi- 
cian attending their patients may be sound asleep to loud 
noises, but are alive and wide awake to the slightest changes 
in their charges. They have lost touch with the whole 
external world, but the ones cared for still have a firm hold 
on them. High as our bridges are raised for the whole 
world, they are low for the ones we care for. 

Let an appreciable change occur in the stimuli to which 
we are awake, an amount of energy immediately is drawn 
from the reserve store, the thresholds barring the entrance 
to the host of intruders are lowered and we are once more 
in communication with the external world, — our sleep is 
gone and we are wide awake. We can thus be wide awake 
in the very depth of our sleep. The possibility of shaking 
off the grip of sleep under appropriate circumstances and 
especially the highly significant fact of wakefulness in the 
very depths of sleep form insuperable difficulties for all 
those plausible, apparently scientific theories of sleep, 
theories based on circulation, engorgement, anemia or hyper- 
emia, narcosis and autointoxication. We can watch in 
our sleep, count the flow of time and awake at the right 
moment. The fact that we can sleep and still watch and 
keep awake in regard to special objects and particular 
persons shows that sleep is not a matter of blood circulation 

1 My work on dreams will be published in a separate essay. 



88 An Experimental Study of Sleep 

or of intoxication by accumulation of waste products in the 
system. Sleep is not a disease, not a pathological process 
due to the accumulation of toxic products in the brain or 
in the system generally. Sleep is not of those fatal uncon- 
trollable onsets characteristic of the morbid processes, such 
as epilepsy, sunstroke, or apoplexy, nor is sleep a sort of 
narcolepsy. Sleep is not a disease, it is not, as the chemical 
speculators would have it, a kind of narcosis of the system 
by the poisons of fatigue products. Sleep is not patho- 
logical, it is essentially physiological in character. We do 
not go to sleep, because we are poisoned and wake up when 
the poisons are eliminated. We go to sleep at our own 
sweet will and can wake at pleasure. We can wake at any 
moment and can even be awake in the very depths of our 
sleep. Sleep is not an abnormal condition, it is a normal 
state. Like the waking states, sleep-states are part and 
parcel of the life-existence of the individual. Waking and 
sleeping are intimately related, — they are two different 
manifestations of one and the same life-process, — one is 
as normal and healthy as the other. One cannot help 
agreeing with Claperede's biological view that sleep is a 
positive function of the organism, that sleep belongs to 
the fundamental instincts. As Claperede forcibly puts it: 
"Le sommeil est une fonction de defense, un instinct qui 
a pour but, en frappant 1'animal d'inertie, de l'e npecher 
de parvenir au stade d'epuisement: ce n'est pas parce que 
nous sommes intoxiques, ou epuises, que nous dormons, 
mais nous dormons pour ne pas l'etre." 

If we look at the matter from a psychological stand- 
point, we may say that sleep is a rise of the thresholds of 
mental aggregates or of moments consciousness. I have 
pointed out in a former work 1 of mine that to minimize the 
expenditure of neuron energy and reach the minimum of 
consciousness constitutes the tendency of psvchomotor life. 
We can fully realize the importance of this tendency, if we 
regard it from a teleological point of view. In the struggle 
for existence or in the economical system of competition of 
modern life the saving of unnecessary expenditure, where 
only possible, is of the highest consequence. Organisms 

1 Multiple personality. 



An Experimental Study of Sleep 89 

that can best effect such an economy of energy will be best 
fitted to survive. Those organisms that are enabled to 
reduce to its minimum the friction and loss of neuron energy 
have the advantage of possessing at their disposal a greater 
amount of energy to cope with new circumstances, with 
novel conditions, and react better and in a more favorable 
way when confronted with changes in their environment. 
This economizing becomes absolutely indispensable in the 
life-existence of higher organisms, the environment of which 
is highly complex. The reduction of psychomotor activity 
to the least amount of psychophysiological expenditure, in 
other words, to the minimum of consciousness is the law of 
psychomotor life in general and of the highest representatives 
of that life in particular. 

I have further pointed out in the same work that this 
economizing is by no means an endless process, there is a 
certain minimum of consciousness beyond which psychic 
states cannot pass. This minimum of consciousness once 
reached, must remain stationary, for a fall below it is the 
arrest of the activity of the mental aggregate. In other 
words, there is a certain minimum below which conscious- 
ness cannot be reduced with impunity. Reduce the con- 
sciousness of the total psychic aggregate by lowering the 
sensibility of its constituents and the whole mental system 
will cease to function. Now under the conditions of mono- 
tony and limitation of psychomotor activity the moment- 
threshold rises until the psychic minimum vanishes and the 
organism is asleep. 

Putting the matter again in teleological terms we may 
say that we go to sleep when we relinquish our hold on the 
relations of our external environment. We fall asleep 
when our consciousness is fagged, when we wish no longer 
to enter into communication with the external world, when 
we lose interest in our surroundings. When our interest 
in external existence fags and fades away, we go to sleep. 
When Our interests in the external world cease, we draw up 
the bridges, so to say, interrupt all external communication, 
as far as it is possible, and become isolated in our own for- 
tress and repair to our own world of organic activity and 
inner dream life. We fall asleep when the vital interests 



90 An Experimental Study of Sleep 

in external being have fallen into the background of con- 
sciousness; we awake when those interests are aroused. 
When the struggle for existence ceases we repair to our 
castle and battlements. Sleep is the interruption of our 
intercourse with the external world ; — it is the laying down 
of our arms for a respite in the struggle of life. Sleep is 
a truce with the world. When all psychomotor reactions 
to the stimuli of the external environment cease, we sleep. 
We sleep, because we are no longer interested to take an 
active part in the battle of life. From a teleological stand- 
point we may say that sleep is a dismissal of the external 
world with all its vicissitudes, troubles and pains. We 
cease to desire, we cease to react, and we sleep and dream 
in peace. 

And when evening descended from heaven above, . 
And the earth was all rest, and the air was all love, 
And delight, tho' less bright, was far more deep 
And the day's veil fell from the world of sleep, 

And the beasts, and the birds, and the insects were drowned 
In an ocean of dreams without a sound; 
Whose waves never mark, tho' they ever impress 
The light sand which paves it, consciousness. 

— Shelter 



Chapter XIII 

Motor Consciousness and Sleep 

THE condition of limitation of voluntary movements 
plays an important role in the induction of sleep 
states. This is due to the fact that motor con- 
sciousness not only forms the main body of our 
mental activity, but also that ideo-motor life is more sub- 
ject to changes from slight stimulations than is our purely 
sensory life. Motor elements are highly plastic and modi- 
fiable; they enter readily into ever new combinations. 
From a biological standpoint one can realize the impor- 
tance of the great modifiability displayed by sensori-motor 
and ideo-motor elements, since in the adaptation of the 
organism to its environment it is these elements that are 
mainly employed in reaction to stimuli of the external 
world. From the standpoint of adaptation a slight differ- 
ence of sensory experience may give a widely different and 
highly complex motor reaction. 

Psychomotor processes form the most important and 
largest portion of mental life. With the exception of man, 
all the representatives of the animal kingdom, from the 
lowest to the highest forms, represent but different stages 
in the evolution of sensori-motor life. The great majority 
of mankind still leads a life closely allied to animal sensori- 
motor states. Instance the delight of children in their 
plays, and the all absorbing interest of college students in 
their baseball and football games. Even in the highest and 
most developed forms of mental activity motor ideas and 
representations are by far the most predominant. With- 
out motor elements ideational life is arrested. It is these 
sensori-motor and ideo-motor elements that constitute the 
" stream, the flow, the current " of our mental life. Motor 
elements enter freely and easily into combinations with all 
other elements of mental life. 

This ease and high plasticity of ideo-motor elements is 
specially well brought out in hypnosis. Sensori-motor and 
ideo-motor suggestions are taken before purely sensory 
suggestions; paralysis, catalepsy, contracture, all kinds of 

9i 



92 An Experimental Study of Sleep 

motor and kinesthetic illusions and hallucinations are 
easily induced even in the very light stages, while it is only 
in the deeper stages that changes of ideo-sensory elements 
can be brought about. The induction of purely ideo-sen- 
sory illusions, hallucinations or delusions, positive and 
negative, can only be effected in the very deep stages of 
hypnosis. The freedom in forming new combinations and 
associations makes the suggestion of motor ideas and repre- 
sentations highly effective. 

Throughout the scale of animal life, from the lowest to 
the highest forms, intelligence is intimately related to the 
degree of development of the muscular system and to the 
delicacy of motor adjustments. Among the lower forms 
of life the Cephalopods are well equipped with powerful 
muscular arms capable of executing a great variety of vigor- 
ous movements. Now the Cephalopods also possess a more 
highly developed nervous system with a higher grade of 
mental functions than the rest of the Mollusca. The 
great activity of ants and bees is notorious and their instinc- 
tive psychic life is the richest among the Arthropoda. Note 
the great variety of motor adjustments of the beaver and 
also of the intelligence that goes along with it. Birds 
possessed of a high degree of activity and motor adapta- 
bility are also the most intelligent of their kind, such for 
instance as the different species of talking birds. Notice 
the activity and great agility of the fox and also the unusual 
cunning for which the animal is so celebrated in song and 
fable. The suppleness of the dog, his quick reactions to 
stimulations, the resources of his motor adjustments and 
the great extent of his modifiability under changing con- 
ditions are all well known and along with them goes a high 
degree of mental activity. Of all the Mammals the Ouad- 
rumana are the most active, the most imitative, and with the 
exception of man, they are also the most intelligent. When 
we come to man we cannot help admiring the high com- 
plexity and extreme delicacy of his motor adjustments. 
Most marvellous however is the human hand, that divine 
organ which gives shape and form to works of art, to all 
outward visible manifestations of civilization. The great 
artists and thinkers of antiquity held the human hand in 



An Experimental Study of Sleep 93 

great veneration. One of the great Greek philosophers 
did not even hesitate to declare that man's superiority over 
the brute was due to his hand. Finally in the wonderfully 
delicate motor adjustments of speech we find clearly illus- 
trated the intimate relation between motor and psychic 
activities. 

Experiments prove the same truth of the importance 
of motor elements in our mental life. If a series of syl- 
lables or numbers is given to memorize, after one reading, 
five out of ten can be remembered, though with some diffi- 
culty; but if the syllables or numbers are written down at 
the same time, though not looked at during the writing, a 
far greater percentage such as six or seven syllables can be 
remembered. If the motor elements in a train of ideas are 
suppressed, the order of the series becomes confused and 
even totally destroyed, showing that the motor ideas are 
important links in trains of association of ideas. Motor 
elements form the nucleus of consciousness. 

Biologically regarded, voluntary activity, will, is the 
power of the organism to adjust itself to the conditions of 
the external environment. In its last psychological analy- 
sis voluntary activity, will, consists of ideo-motor elements, 
of various modes of adaptations. Will, consisting of kin- 
aesthetic elements, constitutes the active subject of per- 
sonality and individuality. If this be realized, then the 
vital importance of motor consciousness cannot be too highly 
overrated. Motor consciousness is at the very heart of per- 
sonality. We are what we can accomplish. Extreme vari- 
ability and adaptability of reactions to environment are 
the main characteristic traits of intelligence, will, person- 
ality. 

The readiness of psycho-motor elements and groups to 
enter into ever new combinations gives rise to the forma- 
tion of a great wealth of associations which help to make 
the labile psycho-motor groups and systems easy of recall. 
In fact it may be said that the ease of recall is proportionate 
to the mass of associated kinesthetic elements. The great 
modifiability and variability of systems of motor elements 
requisite in the adaptation of the organism to the varying 
conditions of life, to its environment, make the ever greater 



94 An Experimental Study of Sleep 

instability of motor elements an imperative necessity in the 
struggle for existence. 

Forming the predominant elements, both as to inten- 
sity and mass, of the most complex, relatively stable, though 
ceaselessly shifting groups and systems, constituting the 
highly developed organization of mental life, the motor 
elements, presentative and representative, are also the first 
to become involved in the process of dissociation. In the 
various forms of nervous and mental diseases, under differ- 
ent conditions of intoxication and auto-intoxication, in the 
traumas caused by shock, physical and psychic, the deli- 
cate movements of adjustment are the first to become affected ; 
dissociations of systems of motor elements are first to occur. 

The instability of psycho- motor elements maybe brought 
in relation with the fact of the early affection of muscular 
and kinesthetic sensitivity and with the predominance of 
sensori-motor over purely sensory symptoms, so frequently 
occurring in the course of nervous diseases. With this 
may be correlated the significant fact referred to bv Mosso 
that " all substances which slowly destroy the organism 
must produce phenomena analogous to those of curari 
since the motor nerves. . . . have less vitality than the 
sensory." It may also be observed in passing that cellular 
kinoplasm with the "kinocentrum," the centrosome and its 
archoplasmic structures, possibly the most primitive organ- 
oids of the cell, similarly manifest a high degree of vari- 
ability and instability. 

Motor elements mav be regarded as the labile consti- 
tuents of consciousness; — they become easily and fre- 
quently dissociated and dropped into the subconscious; but 
for that very reason they are also very easily reproduced 
or regenerated. In this respect motor elements follow the 
general biological law of organic regeneration: Organs 
that are easily and frequently lost in the struggle for exis- 
tence are also easily regenerated, as for instance, the legs 
and claws of Crustacea or the tentacles of the starfish and 
the octopus. Dissociated systems of motor elements often 
become regenerated and under pathological conditions, 
when synthesis is impossible, they may recur with great 
persistence giving rise to the most uncontrollable tvpes of 



An Experimental Study of Sleep 95 

insistent ideas and impulses and to various forms of so- 
called "psychic epilepsy/' especially of the motor type, 
closely mimicking typical organic epilepsy. Such disso- 
ciated, subconscious systems, like rudimentary, aborted 
organs, the appendix, for instance, may often prove very 
injurious to the organism. The recurrence of such sub- 
conscious, submerged, dissociated systems has its parallel 
in the biological phenomena of reversion or atavism. 

The fact that psycho-motor elements enter easily into 
combinations and form extensive associative systems, makes 
them easy of recall and hence persistent in memory. From 
an educational standpoint one realizes the importance of 
this fact. Children learn things best not by abstract notions, 
not by looking at objects and hearing of things, but by 
acting out whatever is taught them. Motor consciousness is 
more vital than sensory. In the training of the mentally 
defective the best method followed is that of motor instruc- 
tion, — to get at the meaning of things by means of action, 
even if it be automatic at first. As a matter of fact even the 
normal and well balanced mind gets at the meaning of things 
by handling them, by having the attributes and qualities 
of the objects and processes to be learned acted out. Acting 
forms the greater part of man s life. 

Forming as motor consciousness, does the very heart of 
mental activity, we can well realize the paramount import- 
ance of the condition of limitation of voluntary movements. 
By limiting the motor activity of the organism we impover- 
ish its mental processes and lower the heart-beat of mental 
life. The active nucleus of psycho-motor reactions becomes 
passive, the organism becomes disabled in its response to the 
stimulations of the external environment, the thresholds rise 
and the organism is no longer in relation with the external 
world. When motor activity with its concomitant motor- 
consciousness becomes lowered, restricted, and fades away, 
the organism becomes necessarily passive and passes into 
sleep. 

Thus monotony and limitation of voluntary movements 
work in one direction, — they tend to raise the thresholds 
of psychomotor reactions, they cooperate in the induction 
of sleep. These conditions are usually brought about natu- 



96 An Experimental Study of Sleep 

rally in the course of the daily or nightly life activity of the 
individual organism, or the conditions may be produced 
artificially. In both cases the result is the same, — the 
organism falls asleep. In the life of higher animals the 
two cases may often combine. When the individual has 
fagged out his life interests in his active relations with his 
surroundings, when the stimuli have become monotonous 
to him and his activity with its correlative motor conscious- 
ness has become limited and lowered, he makes artificial 
arrangements for the intensification of the conditions of 
monotony and limitation of voluntary activity. He seeks 
for a dark nook, closes his eyes to exclude as much as pos- 
sible all extraneous disturbing stimulations and tries to lie 
down quietly and comfortably, restricts his voluntary move- 
ments, breaks his connection with the external world and 
goes to sleep. The organism falls into sleep, when the 
thresholds rise, wakes and rises when the thresholds fall. 

Looked at from a purely physiological standpoint and ex- 
pressed in terms of energy, of the "cell-energy," sleep maybe 
regarded as the onset of fatigue, as the onset of exhaustion of 
the levels of dynamic energy in response to external stimuli. 
The law of stimulus-exhaustion comes here into plav as 
we have indicated in our discussion of cell-energy. Each 
particular stimulus has its maximum amount of energy 
which can be drawn upon, under ordinary conditions of daily 
life. As the special stimulus approaches its limit, it works 
under greater and greater difficulties, draws less <md less 
energy and finally ceases to awaken any response, — the 
threshold is raised to its maximum and the organism, as far 
as that special stimulus is concerned, is no longer awake, — 
the organism is asleep. In the course of its daily activity the 
same takes place in regard to most of the objects, to most 
or to all of the stimuli that constitute the external world of 
the organism. The stimuli of the external world have drawn 
all that was permitted to them on their bank accounts, so 
to say, and the account for the time being is closed. Noth- 
ing more is permitted to go out. No stimulus of ordinary 
life is permitted to draw over and above a certain amount. 
There must always be ready capital for unusual situations, 
for emergencies. When the stimuli have drawn their due 



An Experimental Study of Sleep 97 

and the organism is left with its reserve energy, — libera- 
tion of energy with its accompanying waking states ceases. 
The organism is no longer awake to the stimuli and is 
asleep. 

As in the waking states the katabolic processes predom- 
inate, so in sleep the reverse processes, the anabolic, take the 
upper hand. The organism begins to recuperate its losses 
and fills up the accounts drawn upon by the stimuli of the 
external environment, when in active relation with them. 
With the increase of the income of energy the raised thresh- 
olds begin to fall until a point is reached when the stimuli 
once more overstep the lowered thresholds and once more 
gain access to the stores of life-energy, — the organism 
awakes and enters into active relations with the external 
environment. 

Regarded then from various standpoints, sleep is a 
rise of moments-thresholds under conditions of monotony 
and limitation of voluntary movements. In this respect 
sleep strongly contrasts with hypnosis. In hypnosis the 
individual is specially accessible to any kind of sugges- 
tions coming from the external world, the psycho-motor 
reactions are greatly lightened and are released by the sug- 
gestion or external stimulus with great facility, far greater 
than in the waking state. This great facility is often 
expressed by the statement that in hypnosis the inhibitions 
are removed. What specially characterizes hypnosis is the 
fact of fall of thresholds present in individuals, with a predis- 
position to states of dissociation; in sleep, on the contrary 
we have found from our study, the general characteristic 
is the rise of psycho-motor thresholds. In passing from the 
waking state into the subwaking hypnoidal state the indi- 
vidual may either pass into hypnosis with its dissociated 
states and lowered psycho-motor thresholds or may go into 
sleep with raised psycho-motor thresholds. The process of 
redistribution of thresholds takes place in the intermediary, 
hypnoidal states. When the redistribution of thresholds in 
the hypnoidal states brings about a fall of thresholds due 
to predisposition to and further cultivation of dissociations, 
the result is hypnosis; when the redistribution in the hyp- 
noidal states brings about a rise of thresholds, the result is 
sleep. 



98 An Experimental Study of Sleep 

Biologically regarded, sleep is as much an instinct as 
hunger or sex. 

Phylogenetically and ontogenetically, the sleep-states 
of higher animals are developed out of undifferentiated, 
intermediary, subwaking, hypnoidal-like states found in the 
resting states of the lower representatives of animal life. 
The hypnoidal state is the primitive rest state out of which 
sleep arises. Briefly put, the hypnoidal state is the germ 
of sleep. 

Physiologically and psychologically regarded, sleep is 
an actively induced passive state in relation to the external 
environment; the psycho-physiological systems have their 
thresholds raised in relation to external stimulations; the 
rise of threshold is induced by a mass of impressions pos- 
sessing little or no variability, by limitation or by relative 
withdrawal of stimulations, or what is the same, by monotony 
of stimulations and by limitation of voluntary movements. 



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